Thermal Switch

ABSTRACT

A thermal switch having an on-state and an off-state is provided. First and second plates are composed from a thermally conductive material. The first and second plates are connected to form an internal cavity having a channel defining a gap between the first and second plate. The first reservoir is coupled to the channel and contains a thermally conductive liquid. The actuator is coupled to the first reservoir and the channel and is moveable between a first state and a second state corresponding to the on-state and the off-state of the thermal switch, respectively. Thermally conductive liquid is allowed to flow from the first reservoir to the channel when the actuator is in the first state and allowed to flow from the channel to the first reservoir when the actuator is in the second state.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.17/097,710 filed on Nov. 13, 2020, which is a continuation of U.S.patent application Ser. No. 16/877,369, filed May 18, 2020, which is acontinuation of U.S. patent application Ser. No. 16/877,313, filed May18, 2020, which are hereby incorporated by reference in their entirety.

FIELD OF THE INVENTION

The invention relates generally to thermal switches, and moreparticularly, to a controllable thermal switch that utilizes liquidmetal to vary thermal conductivity between a heat source and a heatsink.

BACKGROUND OF THE INVENTION

Controlling the temperature of machine components or workpieces is animportant and common challenge in industry. Components such as sensors,electronics, vessels for chemical reaction, and batteries often operateoptimally at a specific temperature. Temperature dependent manufacturingprocesses, such as those employed in semiconductor manufacturing, relyon precise control of the temperature of a workpiece to achieve optimalresults.

Temperature control is generally achieved by one or both of: regulatingheat generation, such as with an electric heater, and regulating thetransfer of heat into and out of a system by convection, radiation, andconduction. Of these three modes of heat transfer, thermal conduction isoften the most difficult to control, as it is usually determined only bythe thermal properties of components and the thermal couplings betweencomponents, which typically cannot be changed during operation. Aninability to control thermal conduction means commonly employed thermalcontrol systems face limitations in efficiency, rate of temperaturechange, maximum heat load, or other system performance characteristics.

These limitations may be significant in thermal systems which experiencefluctuating heat loads. Fluctuating heat loads may be caused by avariety of factors, including but not limited to: (a) varying externalenvironmental heat sources, such as a satellite moving in and out ofsunlight, (b) the thermal system operates over a wide range oftemperatures, (c) the thermal system generates a varying heat load (e.g.the battery and inverter of an electric vehicle), (d) the thermal systemrapidly changes the temperature of a component (e.g. some types ofthermal processing or testing), (e) the thermal system is used toalternately heat and cool a component, and (f) the thermal systemrequires a high degree of control precision (e.g. semiconductormanufacturing equipment). For example, some temperature control systemsmay employ a combination of modulated heating with constant cooling, aninefficient control method which limits the performance of a thermalsystem.

Some prior art temperature control systems have utilized various meansof changing thermal conduction between machine components. Such deviceshave often been referred to as thermal switches. Generally, these priorart thermal switch have operated by one of: making and breaking physicalcontact between two surfaces, changing the thermal conductivity across agas-filled gap (most often by manipulating gas pressure), affecting achange in the thermal conductivity of a special material, or moving athermally conductive liquid.

However, the thermal switches found in prior art have shortcomings inone or more of: thermal performance, cost, reliability, and ease ofimplementation. The present invention is aimed at one or more of theproblems identified above.

SUMMARY OF THE INVENTION

In some embodiments, thermal devices and systems incorporating featuresof the present invention may exhibit improved efficiency andperformance. In such thermal devices and systems, precise, rapid,proportional control of thermal conduction may be provided. Devices andsystems incorporating features of the present invention are highlyreliable by virtue of a liquid interface, and achieve a wide range ofcontrolled thermal conductivity, with rangeability as high as 600:1.Such devices can support structural loads and exhibit no externalmovement, which eases implementation.

In a first aspect of the present, a thermal switch having an on-stateand an off-state is provided. The first and second plates are composedfrom a thermally conductive material. The first and second plates areconnected to form an internal cavity having a channel defining a gapbetween the first and second plate. The first reservoir is coupled tothe channel and contains a thermally conductive liquid. The actuator iscoupled to the first reservoir and the channel and is moveable between afirst state and a second state corresponding to the on-state and theoff-state of the thermal switch, respectively. Thermally conductiveliquid is allowed to flow from the first reservoir to the channel whenthe actuator is in the first state and allowed to flow from the channelto the first reservoir when the actuator is in the second state

In a second aspect of the present invention, a thermal switch isprovided. The thermal switch includes first and second plates, adividing plate, first and second reservoir, an actuator. The first plateand second plates are composed from a thermally conductive material andare connected to form an internal cavity having a channel forming a gapbetween the first and second plates. The channel has a first end and asecond end. The dividing plate is positioned between the first andsecond plate and is configured to divide the channel into a plurality ofconduction zones. Each conduction zone has at least one gas entry/exitpoint. The first reservoir is coupled to the first end of the channeland contains a liquid metal. The second reservoir is coupled to thechannel and contains a gas. The actuator is coupled to the firstreservoir and the first end of the channel and is moveable between firstand second states. The first and second reservoirs and the channel formpart of a closed system. The membrane is positioned between the actuatorand the channel and has a first position and a second positionassociated with the first and second states of the actuator,respectively. The membrane is moveable between the first and secondpositions in response to the actuator being switched from the firststate to the second state, The liquid metal is pushed into theconduction zones from the first reservoir as the membrane is moved fromthe second position to the first position, The liquid metal flows fromthe conduction zones to the first reservoir and the gas in the secondreservoir flows into the conduction zones in response to the membranebeing moved from the first position to the second position.

In a third aspect of the present invention, a method is provided. In afirst step, a thermal switch is provided. The thermal switch includes afirst plate, a second plate, a first reservoir and an actuator. Thefirst and second plates are composed from a thermally conductivematerial and are connected to form an internal cavity having a channeldefining a gap between the first and second plate. The first reservoiris coupled to the channel and contains a thermally conductive liquid.The actuator is coupled to the first reservoir and the channel and ismoveable between first and second states. The method further includesthe steps of switching the actuator from the second state to the firststate to push the thermally conductive liquid to flow from the firstreservoir to the channel and switching the actuator from the first stateto the second state to allow the thermally conductive liquid to flowfrom the channel to the first reservoir.

In a fourth aspect of the present invention, a thermal switch isprovided. The thermal switch includes a first plate, a second plate, apost, a channel, a first reservoir, a second reservoir, an actuator anda membrane. The first plate is composed from a thermally conductivematerial and forms a first side of the thermal switch. The second plateis composed from a thermally conductive material and forms a second sideof the thermal switch. The second plate is coupled to the first plate bya plurality of fasteners. The second side, an outer wall extending fromthe second side, and the first side, surround an internal cavity andform a housing. The post extends from an internal surface of the secondside towards the first side. The post, outer wall and second sidedefining a trench. The channel has a first end and a second end and islocated between an internal surface of the first side and an uppersurface of the post. The channel defines a gap between the first andsecond plates. The first reservoir is coupled to the first end of thechannel and contains a thermally conductive liquid. The second reservoiris coupled to the second end of the channel and contains a gas. Theactuator is coupled to the first reservoir and the first end of thechannel. The membrane is positioned between the actuator and the firstend of the channel and is located within the trench. The membrane has afirst position and a second position associated with the first andsecond states of the actuator, respectively. The membrane is moveablebetween the first and second positions in response to the actuator beingswitched from the first state to the second state. The liquid metal ispushed into the gap from the first reservoir and the gas is pushed fromthe gap to the second reservoir as the membrane is moved from the secondposition to the first position. The liquid metal flows from the gap tothe first reservoir and the gas in the second reservoir flows into thegap in response to the membrane being moved from the first position tothe second position.

In a fifth aspect of the present invention, a thermal switch isprovided. The thermal switch includes a first plate, a second plate, ashim, an oxygen seal, a post, a channel, a gas entry/exit point, a firstreservoir, a second reservoir, a dividing plate, an actuator and amembrane. The first plate is composed from a thermally conductivematerial and forms a first side of the thermal switch. The second plateis composed from a thermally conductive material and is coupled to thefirst plate by a plurality of fasteners. The second plate forms a secondside of the thermal switch. An outer wall extends from the second side.The first side, the second side and the outer wall surround an internalcavity and form a housing. The fasteners are located partially in theouter wall of the second plate. The shim is located between the firstand second plates configured to provide thermal isolation therebetween.The oxygen seal is located between the interior surface of the firstplate and an upper surface of the outer wall and is adjacent thefasteners. The post extends from an internal surface of the second sidetowards the first side. The post, outer wall and second side define atrench. The channel has a first end and a second end and is locatedbetween an internal surface of the first plate and an upper surface ofthe post. The channel defines a gap between the first and second plates.The gas entry/exit point is located between the interior surface of thefirst plate and an upper surface of the post. A height of the gasentry/exit point is less than a height of the gap. The first reservoiris coupled to the first end of the channel and contains a thermallyconductive liquid. The second reservoir is coupled to the second end ofthe channel and contains a gas. The dividing plate is positioned betweenthe first and second plates and is configured to divide the channel intoa plurality of conduction zones. The actuator is coupled to the firstreservoir and the first end of the channel. The actuator is locatedwithin the trench and surrounds the post. The membrane is positionedbetween the actuator and the first end of the channel and is locatedwithin the trench. The membrane has a first position and a secondposition associated with the first and second states of the actuator,respectively. The membrane is moveable between the first and secondpositions in response to the actuator being switched from the firststate to the second state. The thermally conductive liquid is pushedinto the gap from the first reservoir as the membrane is moved from thesecond position to the first position, wherein the thermally conductiveliquid flows from the gap to the first reservoir and the gas in thesecond reservoir flows into the gap in response to the membrane beingmoved from the first position to the second position.

In a sixth aspect of the present invention, a thermal switch isprovided. The thermal switch includes a first plate, a second plate, ashim, an oxygen seal, a post, a channel, a gas entry/exit point, a firstreservoir, a second reservoir, a dividing plate, an actuator and amembrane. The first plate is composed from a thermally conductivematerial and forms a first side of the thermal switch. The second plateis composed from a thermally conductive material and is coupled to thefirst plate by a plurality of fasteners. The second plate forms a secondside of the thermal switch. An outer wall extends from the second side.The first side, the second side and the outer wall surround an internalcavity and form a housing. The fasteners are located partially in theouter wall of the second plate. The shim is located between the firstand second plates and is configured to provide thermal isolationtherebetween. The oxygen seal is located between the interior surface ofthe first plate and an upper surface of the outer wall and adjacent thefasteners. The post extends from an internal surface of the second sidetowards the first side. The post, outer wall and second side define atrench. The channel has a first end and a second end and is locatedbetween an internal surface of the first plate and an upper surface ofthe post. The channel defines a gap between the first and second plates.The gas entry/exit point is located between the interior surface of thefirst plate and an upper surface of the post. A height of the gasentry/exit point is less than a height of the gap. The first reservoiris coupled to the first end of the channel and contains a thermallyconductive liquid. The second reservoir is coupled to the second end ofthe channel and contains a gas. The dividing plate is positioned betweenthe first and second plates and is configured to divide the channel intoa plurality of conduction zones. The actuator is coupled to the firstreservoir and the first end of the channel. The actuator is locatedwithin the trench and surrounds the post. The membrane is positionedbetween the actuator and the first end of the channel and is locatedwithin the trench. The membrane has a first position and a secondposition associated with the first and second states of the actuator,respectively. The membrane is moveable between the first and secondpositions in response to the actuator being switched from the firststate to the second state. The thermally conductive liquid is pushedinto the gap from the first reservoir as the membrane is moved from thesecond position to the first position. The thermally conductive liquidflows from the gap to the first reservoir and the gas in the secondreservoir flows into the gap in response to the membrane being movedfrom the first position to the second position.

In a seventh aspect of the present invention, a method is provided. Themethod includes the step of providing a thermal switch. The thermalswitch includes first and second plates, a post, a channel, first andsecond reservoirs, an actuator and a membrane. The first plate iscomposed from a thermally conductive material and forms a first side ofthe thermal switch. The second plate is composed from a thermallyconductive material and forms a second side of the thermal switch. Thesecond plate is coupled to the first plate by a plurality of fasteners.The second side, an outer wall extending from the second side, and thefirst side, surround an internal cavity and form a housing. The postextends from an internal surface of the second side towards the firstside. The post, the outer wall and the second side define a trench. Thechannel has a first end and a second end and is located between aninternal surface of the first side and an upper surface of the post. Thechannel defines a gap between the first and second plates. The firstreservoir is coupled to the first end of the channel and contains athermally conductive liquid. The second reservoir is coupled to thesecond end of the channel and contains a gas. The actuator is coupled tothe first reservoir and the first end of the channel. The membrane ispositioned between the actuator and the first end of the channel and islocated within the trench. The membrane has a first position and asecond position associated with the first and second states of theactuator, respectively. The membrane is moveable between the first andsecond positions in response to the actuator being switched from thefirst state to the second state. The thermally conductive liquid ispushed into the gap from the first reservoir and the gas is pushed fromthe gap to the second reservoir as the membrane is moved from the firstposition to the second position. The thermally conductive liquid flowsfrom the gap to the first reservoir and the gas in the second reservoirflows into the gap in response to the membrane being moved from thesecond position to the first position. The method further includes thestep of switching the actuator from the second state to the first stateto push the thermally conductive liquid into the gap from the firstreservoir, wherein the gas is pushed from the gap to the secondreservoir as the membrane is moved from the second position to the firstposition. The method also includes the step of switching the actuatorfrom the first state to the second state to allow the thermallyconductive liquid to flow from the gap to the first reservoir, whereinthe gas in the second reservoir flows into the gap in response to themembrane being moved from the first position to the second position.

In an eighth aspect of the present invention, a seal for use with adevice having a housing forming an internal cavity is provided. Thehousing has an interface that connects the internal cavity to anexternal environment. The seal includes a sealing component and anabsorbing component. The sealing component is located within the housingand is coupled to the interface. The sealing component is configured torestrict entry of a gas from the external environment to the internalcavity. The absorbing component is located within the housing betweenthe sealing component and the internal cavity and is configured toabsorb any gas that passes the sealing component.

In a ninth aspect of the present invention, a seal for use with athermal device having first and second plates that form a housing isprovided. The housing forms an internal cavity. The housing has aninterface that connects the internal cavity to an external environmentand is formed by a seam between the first and second plates. The seamtraverses an outer perimeter of the housing. The seal includes a sealingcomponent and an absorbing component. The sealing component is locatedwithin the housing and is coupled to the interface. The sealingcomponent is configured to restrict entry of a gas from the externalenvironment to the internal cavity and includes a first trench withinthe housing and an isolating element. The first trench is coupled to theinterface and surrounds the internal cavity. The first trench contains agas blocking material. The isolating element extends from the one of thefirst and second plates into the first trench forming a gap between theisolating element and the other one of the first and second plates. Theabsorbing component is located within the housing between the sealingcomponent and the internal cavity and is configured to absorb any gasthat passes the sealing component. The absorbing component includes asecond trench within the housing. The second trench is coupled to theinterface and surrounds the internal cavity.

In a tenth aspect of the present invention, a thermal device havingfirst and second plates is provided. The second plate is coupled to thefirst plate forming a housing. The housing forms an internal cavity andhas an interface that connects the internal cavity to an externalenvironment. The interface is formed by a seam between the first andsecond plates and traverses an outer perimeter of the housing. Thesealing component is located within the housing and is coupled to theinterface. The sealing component is configured to restrict entry of agas from the external environment to the internal cavity. The absorbingcomponent is located within the housing between the sealing componentand the internal cavity and is configured to absorb any gas that passesthe sealing component.

In an eleventh aspect of the present invention, a thermal device isprovided. The thermal device includes a first plate, a second plate, asealing component and an absorbing component. The second plate iscoupled to the first plate forming a housing. The housing forms aninternal cavity and has an interface that connects the internal cavityto an external environment. The interface is formed by a seam betweenthe first and second plates. The seam traverses an outer perimeter ofthe housing. The sealing component is located within the housing,coupled to the interface and configured to restrict entry of a gas fromthe external environment to the internal cavity. The sealing componentincludes a first trench within the housing and an isolating element. Thefirst trench is coupled to the interface and surrounds the internalcavity. The first trench contains a gas blocking material. The isolatingelement extends from the one of the first and second plates into thefirst trench forming a gap between the isolating element and the otherone of the first and second plates. The absorbing component is locatedwithin the housing between the sealing component and the internal cavityand is configured to absorb any gas that passes the sealing component.The absorbing component includes a second trench within the housing. Thesecond trench is coupled to the interface and surrounds the internalcavity.

In a twelfth aspect of the present invention, a thermal device forcontrolling a temperature associated with a controlled component isprovided. The thermal device includes a thermal switch and a heat sink.The thermal switch having an on-state and an off-state and including afirst plate and a second plate. The first plate is thermally coupled tothe controlled component. The heat sink is coupled to the second plate.The first plate and second plates are composed from a thermallyconductive material. The first and second plates are connected to forman internal cavity having a channel defining a gap between the first andsecond plates. The thermal switch further includes a first reservoir andan actuator. The first reservoir is coupled to the channel and containsa thermally conductive liquid. The actuator is coupled to the firstreservoir and the channel and is being moveable between a first stateand a second state corresponding to the on-state and the off-state ofthe thermal switch, respectively. The actuator is configured to allowthe thermally conductive liquid to flow from the reservoir to thechannel when the actuator is in the first state and to allow thethermally conductive liquid to flow from the channel to the firstreservoir when the actuator is in the second state.

In a thirteenth aspect of the present invention, a thermal deviceincluding a thermoelectric cooler, a thermal switch, a heat sink, afirst reservoir and an actuator is provided. The thermal switch has anon-state and an off-state and includes a first plate and a second platecomposed from a thermally conductive material. The first plate isthermally coupled to the thermoelectric cooler. The heat sink is coupledto the second plate. The first and second plates are connected to forman internal cavity having a channel defining a gap between the first andsecond plates. The first reservoir is coupled to the channel andcontains a thermally conductive liquid. The actuator is coupled to thefirst reservoir and the channel and is moveable between a first stateand a second state corresponding to the on-state and the off-state ofthe thermal switch, respectively. The actuator is configured to allowthe thermally conductive liquid to flow from the reservoir to thechannel when the actuator is in the first state and to allow thethermally conductive liquid to flow from the channel to the firstreservoir when the actuator is in the second state.

In a fourteenth aspect of the present invention, a thermal device forcontrolling a temperature associated with a heat source is provided. Thethermal device includes a thermal switch which has an on-state and anoff-state and first and second plates composed from a thermallyconductive material. The first plate is coupled to the heat source. Thethermal device includes a plurality of cooling channels in the secondplate acting as a heat sink. The first and second plates are connectedto form an internal cavity having a channel defining a gap between thefirst and second plates. The thermal switch includes a first reservoirand an actuator. The first reservoir is coupled to the channel andcontains a thermally conductive liquid. The actuator is coupled to thefirst reservoir and the channel and is moveable between a first stateand a second state corresponding to the on-state and the off-state ofthe thermal switch, respectively, and is configured to allow thethermally conductive liquid to flow from the reservoir to the channelwhen the actuator is in the first state and to allow the thermallyconductive liquid to flow from the channel to the first reservoir whenthe actuator is in the second state.

In a fifteenth aspect of the present invention, a thermal device forcontrolling a temperature associated with a workpiece is provided. Thethermal device includes a heating device and a thermal switch. Theheating device is coupled to the workpiece. The thermal switch has anon-state and an off-state and includes a first plate and a second platecomposed from a thermally conductive material. The first plate isthermally coupled to the heating device. The thermal switch furtherincludes a plurality of cooling channels, a first reservoir and anactuator. The plurality of cooling channels are located in the secondplate and act as a heat sink. The first and second plates are connectedto form an internal cavity having a channel defining a gap between thefirst and second plate. The first reservoir is coupled to the channeland contains a thermally conductive liquid. The actuator is coupled tothe first reservoir and the channel and is moveable between a firststate and a second state corresponding to the on-state and the off-stateof the thermal switch, respectively, and is configured to allow thethermally conductive liquid to flow from the reservoir to the channelwhen the actuator is in the first state and to allow the thermallyconductive liquid to flow from the channel to the first reservoir whenthe actuator is in the second state.

In a sixteenth aspect of the present invention, a thermal device isprovided. The thermal device includes a thermal switch and a firstliquid-based thermal coupling device. The thermal switch has an on-stateand an off-state and includes first and second plates. The firstliquid-based thermal coupling device is coupled to the first plate. Thefirst and second plates are connected to form an internal cavity havinga channel defining a gap between the first and second plate. The thermalswitch further includes a first reservoir, an actuator and a secondliquid-based thermal coupling device. The first reservoir is coupled tothe channel and contains a thermally conductive liquid. The actuator iscoupled to the first reservoir and the channel and is moveable between afirst state and a second state corresponding to the on-state and theoff-state of the thermal switch, respectively, and is configured toallow the thermally conductive liquid to flow from the reservoir to thechannel when the actuator is in the first state and to allow thethermally conductive liquid to flow from the channel to the firstreservoir when the actuator is in the second state. The secondliquid-based thermal coupling device is coupled to the second plate. Thefirst and second liquid-based thermal coupling devices and the thermalswitch form a variable liquid-liquid heat exchanger.

In a seventeenth aspect of the present invention, a thermal device forcontrolling a temperature associated with a working surface is provided.The thermal device includes first and second plates composed from athermally conductive material, the first and second plates are connectedto form first and second internal cavities. One of the first and secondplates includes an outer surface that forms the working surface. Athermal switch is located within each internal cavity. Each thermalswitch has an on-state and an off-state and at least one of the switchesincludes a channel, a first reservoir and an actuator. The channeldefines a gap in the respective internal cavity between the first andsecond plates. The first reservoir is coupled to the channel andcontains a thermally conductive liquid. The actuator is coupled to thefirst reservoir and the channel and is moveable between a first stateand a second state corresponding to the on-state and the off-state ofthe thermal switch, respectively. The actuator is configured to allowthe thermally conductive liquid to flow from the reservoir to thechannel when the actuator is in the first state and to allow thethermally conductive liquid to flow from the channel to the firstreservoir when the actuator is in the second state.

In an eighteenth aspect of the present invention, a thermal device isprovided. The thermal device includes first and second plates composedfrom a thermally conductive material. The first and second plates areconnected by a plurality of fasteners to form first and second internalcavities. One of the first and second plates includes an outer surfacethat forms the working surface. The thermal device further includes athermal switch located in each internal cavity. Each thermal switch hasan on-state and an off-state and first and second sides, at least one ofthe thermal switches including:

a post extending from an internal surface of the second side towards thefirst side, the post and the second side defining a trench;

a channel having a first end and a second end and being located betweenan internal surface of the first side and an upper surface of the post,the channel defining a gap between the first and second plates;

a first reservoir coupled to the first end of the channel and containinga thermally conductive liquid;

a second reservoir coupled to the second end of the channel andcontaining a gas;

an actuator coupled to the first reservoir and the first end of thechannel; and

a membrane positioned between the actuator and the first end of thechannel and being located within the trench, the membrane having a firstposition and a second position associated with the first and secondstates of the actuator, respectively, the membrane being moveablebetween the first and second positions in response to the actuator beingswitched from the first state to the second state, wherein the thermallyconductive liquid is pushed into the gap from the first reservoir andthe gas is pushed from the gap to the second reservoir as the membraneis moved from the second position to the first position, wherein thethermally conductive liquid flows from the gap to the first reservoirand the gas in the second reservoir flows into the gap in response tothe membrane being moved from the first position to the second position.

In a nineteen aspect of the present invention, a thermal device isprovided. The thermal device includes first and second plates composedfrom a thermally conductive material. The first and second plates areconnected by a plurality of fasteners to form first and second internalcavities. One of the first and second plates includes an outer surfacethat forms the working surface. The thermal device further includes athermal switch in each of the internal cavities, a shim located betweenthe first and second plates configured to provide thermal isolationtherebetween and an oxygen seal located between the interior surface ofthe first plate and an upper surface of an outer wall and adjacent thefasteners. Each thermal switch has an on-state and an off-state andfirst and second sides. At least one of the thermal switches including:

a post extending from an internal surface of the second side towards thefirst side, the post, outer wall and second side defining a trench;

a channel having a first end and a second end and being located betweenan internal surface of the first plate and an upper surface of the post,the channel defining a gap between the first and second plates;

a gas entry/exit point located between the interior surface of the firstplate and an upper surface of the post, wherein a height of the gasentry/exit point is less than a height of the gap,

a first reservoir coupled to the first end of the channel and containinga thermally conductive liquid;

a second reservoir coupled to the second end of the channel andcontaining a gas;

a dividing plate positioned between the first and second plates andconfigured to divide the channel into a plurality of conduction zones;

an actuator coupled to the first reservoir and the first end of thechannel, the actuator being located within the trench and surroundingthe post;

a membrane positioned between the actuator and the first end of thechannel and being located within the trench, the membrane having a firstposition and a second position associated with the first and secondstates of the actuator, respectively, the membrane being moveablebetween the first and second positions in response to the actuator beingswitched from the first state to the second state, wherein the thermallyconductive liquid is pushed into the gap from the first reservoir as themembrane is moved from the second position to the first position,wherein the thermally conductive liquid flows from the gap to the firstreservoir and the gas in the second reservoir flows into the gap inresponse to the membrane being moved from the first position to thesecond position.

In a twentieth aspect of the present invention, a thermal device isprovided. The thermal device includes first and second plates composedfrom a thermally conductive material. The first and second plates areconnected by a plurality of fasteners to form first and second internalcavities. One of the first and second plates includes an outer surfacethat forms the working surface. The thermal device further includes ashim, an oxygen seal and a thermal switch located in each internalcavity. The shim is located between the first and second plates and isconfigured to provide thermal isolation therebetween. The oxygen seal islocated between the interior surface of the first plate and an uppersurface of an outer wall and adjacent the fasteners. Each thermal switchhas an on-state and an off-state and first and second sides. At leastone of the thermal switches including:

a post extending from an internal surface of the second side towards thefirst side, the post, outer wall and second side defining a trench;

a channel having a first end and a second end and being located betweenan internal surface of the first plate and an upper surface of the post,the channel defining a gap between the first and second plates;

a gas entry/exit point located between the interior surface of the firstplate and an upper surface of the post, wherein a height of the gasentry/exit point is less than a height of the gap;

a first reservoir coupled to the first end of the channel and containinga thermally conductive liquid;

a second reservoir coupled to the second end of the channel andcontaining a gas;

a dividing plate positioned between the first and second plates andconfigured to divide the channel into a plurality of conduction zones;

an actuator coupled to the first reservoir and the first end of thechannel, the actuator being located within the trench and surroundingthe post; and,

a membrane positioned between the actuator and the first end of thechannel and being located within the trench, the membrane having a firstposition and a second position associated with the first and secondstates of the actuator, respectively, the membrane being moveablebetween the first and second positions in response to the actuator beingswitched from the first state to the second state, wherein the thermallyconductive liquid is pushed into the gap from the first reservoir as themembrane is moved from the second position to the first position,wherein the thermally conductive liquid flows from the gap to the firstreservoir and the gas in the second reservoir flows into the gap inresponse to the membrane being moved from the first position to thesecond position.

In a twenty-first aspect of the present invention, a thermal switchhaving first and second plates, a first reservoir and a pneumaticactuator is provided. The first and second plates are composed from athermally conductive material and are connected to form an internalcavity. The internal cavity has a channel defining a gap between thefirst and second plate. The first reservoir is coupled to the channeland contains a thermally conductive liquid. The pneumatic actuator iscoupled to the first reservoir and the channel and is moveable between afirst state and a second state corresponding to the on-state and theoff-state of the thermal switch, respectively. The pneumatic actuationis configured to allow the thermally conductive liquid to flow from thefirst reservoir to the channel when the pneumatic actuator is in thefirst state and to allow the thermally conductive liquid to flow fromthe channel to the first reservoir when the actuator is in the secondstate.

In a twenty-second aspect of the present invention, a thermal switch isprovided. The thermal switch includes first and second plates composedfrom a thermally conductive material. The first and second plates areconnected to form an internal cavity having a channel forming a gapbetween the first and second plates. The channel has a first end and asecond end. The thermal switch further includes a dividing plate, firstand second reservoirs, a pneumatic actuator and a membrane. The dividingplate is positioned between the first and second plates and isconfigured to divide the channel into a plurality of conduction zones.Each conduction zone having at least one gas entry/exit point. The firstreservoir is coupled to the first end of the channel and contains aliquid metal. The second reservoir is coupled to the channel andcontains a gas. The pneumatic actuator is coupled to the first reservoirand the first end of the channel. The actuator is moveable between firstand second states. The first reservoir, second reservoir and the channelform part of a closed system. The membrane is positioned between theactuator and the channel and has a first position and a second positionassociated with the first and second states of the pneumatic actuator,respectively. The membrane is moveable between the first and secondpositions in response to the pneumatic actuator being switched from thefirst state to the second state. The liquid metal is pushed into theconduction zones from the first reservoir as the membrane is moved fromthe second position to the first position. The liquid metal flows fromthe conduction zones to the first reservoir and the gas in the secondreservoir flows into the conduction zones in response to the membranebeing moved from the first position to the second position.

In a twenty-third aspect of the present invention, a process modulehaving a processing chamber and a thermal switch is provided. Theprocessing chamber receives a semiconductor wafer. The thermal switch iscoupled to the processing chamber and includes first and second plates,a first reservoir and an actuator. The first and second plates arecomposed from a thermally conductive material and are connected to forman internal cavity having a channel defining a gap between the first andsecond plate. The first reservoir is coupled to the channel and containsa thermally conductive liquid. The actuator is coupled to the firstreservoir and the channel and is moveable between a first state and asecond state corresponding to the on-state and the off-state of thethermal switch, respectively. The actuator is configured to allow thethermally conductive liquid to flow from the first reservoir to thechannel when the actuator is in the first state and to allow thethermally conductive liquid to flow from the channel to the firstreservoir when the actuator is in the second state.

In a twenty-fourth aspect of the present invention, an inductivelycoupled plasma process module is provided. The inductively coupledplasma process module includes a processing chamber and a retentiondevice. The processing chamber is configured to receive a semiconductorwafer and has a vessel and a ceramic plate. The vessel and the ceramicplate form an internal plasma cavity. The retention device is locatedwithin the internal plasma cavity and configured to hold and/or supportthe semiconductor wafer in place. The retention device includes aretention device temperature control assembly having a thermal switchcoupled to the processing chamber. The thermal switch includes first andsecond plates composed from a thermally conductive material, a firstreservoir and an actuator. The first and second plates are connected toform an internal cavity having a channel defining a gap between thefirst and second plates. The first reservoir is coupled to the channeland contains a thermally conductive liquid. The actuator is coupled tothe first reservoir and the channel and is moveable between a firststate and a second state corresponding to the on-state and the off-stateof the thermal switch, respectively. The actuator is configured to allowthe thermally conductive liquid to flow from the first reservoir to thechannel when the actuator is in the first state and to allow thethermally conductive liquid to flow from the channel to the firstreservoir when the actuator is in the second state.

In a twenty-fifth aspect of the present invention, a capacitivelycoupled plasma process module is provided. The capacitively coupledplasma process module includes a processing chamber, a top electrode anda retention device. The processing chamber has an internal plasma cavityand is configured to receive a semiconductor wafer. The top electrode islocated within the internal plasma cavity and has a top electrodetemperature control assembly. The retention device is located within theinternal plasma cavity and is configured to hold the semiconductor waferin place. The retention device includes a retention device temperaturecontrol assembly. Either or both of the top electrode temperaturecontrol assembly and the retention device temperature control assemblyinclude a thermal switch. Each of the of the thermal switches includesfirst and second plates composed from a thermally conductive material, afirst reservoir and an actuator. The first and second plates areconnected to form an internal cavity having a channel defining a gapbetween the first and second plates. The first reservoir is coupled tothe channel and contains a thermally conductive liquid. The actuator iscoupled to the first reservoir and the channel and is moveable between afirst state and a second state corresponding to the on-state and theoff-state of the thermal switch, respectively. The actuator isconfigured to allow the thermally conductive liquid to flow from thefirst reservoir to the channel when the actuator is in the first stateand to allow the thermally conductive liquid to flow from the channel tothe first reservoir when the actuator is in the second state.

In a twenty-sixth aspect of the present invention, a thermal switchhaving an on-state and an off-state is provided. The thermal switchincludes first and second plates, a first reservoir, an actuationreservoir and a membrane. The first and second plates are composed froma thermally conductive material. The first and second plates areconnected to form an interior cavity having a channel defining a gapbetween the first and second plate. The first reservoir is coupled tothe channel and contains a thermally conductive liquid. The actuationreservoir contains an actuating material. The membrane is connected tothe first and/or second plate and separates the first reservoir andactuating reservoir. The membrane is moveable between a first state anda second state corresponding to the on-state and the off-state of thethermal switch, respectively. The actuating material expands when heatedand expansion of the actuating material causes the membrane to move fromthe first state to the second state. The thermally conductive liquidflows from the first reservoir to the channel when the actuator is inthe first state and the thermally conductive liquid flows from thechannel to the first reservoir when the actuator is in the second state.

In a twenty-seventh aspect of the present invention, a thermal switch isprovided. The thermal switch includes:

a first plate being composed from a thermally conductive material;

a second plate being composed from a thermally conductive material, thefirst and second plates being connected to form an internal cavityhaving a channel forming a gap between the first and second plates, thechannel having a first end and a second end;

a dividing plate positioned between the first and second plates andbeing configured to divide the channel into a plurality of conductionzones, each conduction zone having at least one gas entry/exit point;

a first reservoir coupled to the first end of the channel, the firstreservoir containing a liquid metal;

a second reservoir coupled to the channel, the second reservoircontaining a gas;

a passive actuator coupled to the first reservoir and the first end ofthe channel, the passive actuator being moveable between first andsecond states, the first reservoir, second reservoir and the channelforming part of a closed system; and,

a membrane positioned between the actuator and the channel and having afirst position and a second position associated with the first andsecond states of the passive actuator, respectively, the membrane beingmoveable between the first and second positions in response to thepassive actuator being switched from the first state to the secondstate, wherein the liquid metal is pushed into the conduction zones fromthe first reservoir as the membrane is moved from the second position tothe first position, wherein the liquid metal flows from the conductionzones to the first reservoir and the gas in the second reservoir flowsinto the conduction zones in response to the membrane being moved fromthe first position to the second position.

Clauses Thermal Switch Clauses

1. A thermal switch, comprising:

a first plate being composed from a thermally conductive material andforming a first side of the thermal switch;

a second plate being composed from a thermally conductive material andforming a second side of the thermal switch, the second plate beingcoupled to the first plate by a plurality of fasteners, wherein thesecond side, an outer wall extending from the second side, and the firstside, surround an internal cavity and form a housing;

a post extending from an internal surface of the second side towards thefirst side, the post, outer wall and second side defining a trench;

a channel having a first end and a second end and being located betweenan internal surface of the first side and an upper surface of the post,the channel defining a gap between the first and second plates;

a first reservoir coupled to the first end of the channel and containinga thermally conductive liquid;

a second reservoir coupled to the second end of the channel andcontaining a gas;

an actuator coupled to the first reservoir and the first end of thechannel; and

a membrane positioned between the actuator and the first end of thechannel and being located within the trench, the membrane having a firstposition and a second position associated with the first and secondstates of the actuator, respectively, the membrane being moveablebetween the first and second positions in response to the actuator beingswitched from the first state to the second state, wherein the thermallyconductive liquid is pushed into the gap from the first reservoir andthe gas is pushed from the gap to the second reservoir as the membraneis moved from the second position to the first position, wherein thethermally conductive liquid flows from the gap to the first reservoirand the gas in the second reservoir flows into the gap in response tothe membrane being moved from the first position to the second position.

2. A thermal switch, as set forth in clause 1, further comprising a shimlocated between the first and second plates configured to providethermal isolation therebetween.

3. A thermal switch, as set forth in clause 1, wherein the fasteners arelocated partially in the outer wall of the second plate, the thermalswitch further comprising an oxygen seal located between the interiorsurface of the first plate and an upper surface of the outer wall andadjacent the fasteners opposite the outer wall.

4. A thermal switch, as set forth in clause 1, wherein the secondreservoir is located within the post.

5. A thermal switch, as set forth in clause 1, further comprising a gasentry/exit point between the second reservoir and the channel.

6. A thermal switch, as set forth in clause 5, wherein the gasentry/exit point is located between the interior surface of the firstplate and an upper surface of the post.

7. A thermal switch, as set forth in clause 6, wherein a height of thegas entry/exit point is less than a height of the gap.

8. A thermal switch, as set forth in clause 1, wherein the gap definesat least one conduction zone within the channel, the at least oneconduction zone has a length of less than or equal to 0.5 inches.

9. A thermal switch, as set forth in clause 1, wherein the gap definesat least one conduction zone within the channel, the at least oneconduction zone has a length of less than or equal to 0.2 inches.

10. A thermal switch, as set forth in clause 1, wherein the gap definesat least one conduction zone within the channel, the at least oneconduction zone has a length of less than or equal to 0.1 inches.

11. A thermal switch, as set forth in clause 1, wherein the gap has aheight of less than or equal to 0.2 inches.

12. A thermal switch, as set forth in clause 1, further comprising adividing plate positioned between the first and second plates andconfigured to divide the channel into a plurality of conduction zones,each conduction zone having at least one gas entry/exit point, each ofthe at least one gas entry/exit points being configured to minimizeentry of the thermally conductive liquid into the at least one gasentry/exit point.

13. A thermal switch, as set forth in clause 1, wherein the actuatorincludes an electric solenoid.

14. A thermal switch, as set forth in clause 1, wherein the actuatorincludes a pneumatic actuator.

15. A thermal switch, comprising:

a first plate being composed from a thermally conductive material andforming a first side of the thermal switch;

a second plate being composed from a thermally conductive material andbeing coupled to the first plate by a plurality of fasteners, the secondplate forming a second side of the thermal switch and an outer wallextending from the second side, wherein the first side, the second sideand the outer wall surround an internal cavity and form a housing,wherein the fasteners are located partially in the outer wall of thesecond plate;

a shim located between the first and second plates configured to providethermal isolation therebetween;

an oxygen seal located between the interior surface of the first plateand an upper surface of the outer wall and adjacent the fasteners.

a post extending from an internal surface of the second side towards thefirst side, the post, outer wall and second side defining a trench;

a channel having a first end and a second end and being located betweenan internal surface of the first plate and an upper surface of the post,the channel defining a gap between the first and second plates;

a gas entry/exit point located between the interior surface of the firstplate and an upper surface of the post, wherein a height of the gasentry/exit point is less than a height of the gap,

a first reservoir coupled to the first end of the channel and containinga thermally conductive liquid;

a second reservoir coupled to the second end of the channel andcontaining a gas;

a dividing plate positioned between the first and second plates andconfigured to divide the channel into a plurality of conduction zones;

an actuator coupled to the first reservoir and the first end of thechannel, the actuator being located within the trench and surroundingthe post;

a membrane positioned between the actuator and the first end of thechannel and being located within the trench, the membrane having a firstposition and a second position associated with the first and secondstates of the actuator, respectively, the membrane being moveablebetween the first and second positions in response to the actuator beingswitched from the first state to the second state, wherein the thermallyconductive liquid is pushed into the gap from the first reservoir as themembrane is moved from the second position to the first position,wherein the thermally conductive liquid flows from the gap to the firstreservoir and the gas in the second reservoir flows into the gap inresponse to the membrane being moved from the first position to thesecond position.

16. A thermal switch, as set forth in clause 15, wherein the trenchextends around a periphery of the second plate and surrounds the post,wherein the actuator is located within the trench.

17. A thermal switch, as set forth in clause 16, wherein the actuatorincludes an electric solenoid having a solenoid coil and a circularplunger, wherein the solenoid coil surrounds and is concentric with thepost, the circular plunger being located adjacent, and being concentricwith, the solenoid coil.

18. A thermal switch, as set forth in clause 16, wherein the actuator isa pneumatic actuator including a plunger, a bellows coupled to theplunger and to a source of pressurized air.

19. A thermal switch, as set forth in clause 15, wherein the secondreservoir is located within the post.

20. A thermal switch, as set forth in clause 15, wherein the gap definesat least one conduction zone within the channel, the at least oneconduction zone has a length of less than or equal to 0.5 inches.

21. A thermal switch, as set forth in clause 15, wherein the gap has aheight of less than or equal to 0.2 inches.

22. A thermal switch, comprising:

a first plate being composed from a thermally conductive material andforming a side of the thermal switch;

a second plate being composed from a thermally conductive material andbeing coupled to the first plate by a plurality of fasteners, the secondplate forming a second side of the thermal switch and an outer wallextending from the second side, wherein the first side, the second sideand the outer wall surround an internal cavity and form a housing,wherein the fasteners are located partially in the outer wall of thesecond plate;

a shim located between the first and second plates configured to providethermal isolation therebetween;

an oxygen seal located between the interior surface of the first plateand an upper surface of the outer wall and adjacent the fasteners.

a post extending from an internal surface of the second side towards thefirst side, the post, outer wall and second side defining a trench, thetrench being located within a central area of the thermal switch, thepost surrounding the trench;

a channel having a first end and a second end and being located betweenan internal surface of the first plate and an upper surface of the post,the channel defining a gap between the first and second plates;

a gas entry/exit point located between the interior surface of the firstplate and an upper surface of the post, wherein a height of the gasentry/exit point is less than a height of the gap,

a first reservoir coupled to the first end of the channel and containinga thermally conductive liquid;

a second reservoir coupled to the second end of the channel andcontaining a gas;

a dividing plate positioned between the first and second plates andconfigured to divide the channel into a plurality of conduction zones;

an actuator coupled to the first reservoir and the first end of thechannel, the actuator being located within the trench; and,

a membrane positioned between the actuator and the first end of thechannel and being located within the trench, the membrane having a firstposition and a second position associated with the first and secondstates of the actuator, respectively, the membrane being moveablebetween the first and second positions in response to the actuator beingswitched from the first state to the second state, wherein the thermallyconductive liquid is pushed into the gap from the first reservoir as themembrane is moved from the second position to the first position,wherein the thermally conductive liquid flows from the gap to the firstreservoir and the gas in the second reservoir flows into the gap inresponse to the membrane being moved from the first position to thesecond position.

23. A thermal switch, as set forth in clause 22, wherein the trenchextends around a periphery of the second plate and surrounds the post,wherein the actuator is located within the trench.

24. A thermal switch, as set forth in clause 23, wherein the actuatorincludes an electric solenoid having a solenoid coil and a circularplunger, wherein the solenoid coil surrounds and is concentric with thepost, the circular plunger being located adjacent, and being concentricwith, the solenoid coil.

25. A thermal switch, as set forth in clause 23, wherein the actuator isa pneumatic actuator including a plunger, a bellows coupled to theplunger and to a source of pressurized air.

26. A thermal switch, as set forth in clause 23, wherein the secondreservoir is located within the post.

27. A thermal switch, as set forth in clause 22, wherein the gap definesat least one conduction zone within the channel, the at least oneconduction zone has a length of less than or equal to 0.5 inches.

28. A thermal switch, as set forth in clause 22, wherein the gap has aheight of less than or equal to 0.2 inches.

29. A method, including the steps of:

providing a thermal switch, the thermal switch include first and secondplates, a post, a channel, first and second reservoirs, an actuator anda membrane, the first plate being composed from a thermally conductivematerial and forming a first side of the thermal switch, the secondplate being composed from a thermally conductive material and forming asecond side of the thermal switch, the second plate being coupled to thefirst plate by a plurality of fasteners, wherein the second side, anouter wall extending from the second side, and the first side, surroundan internal cavity and form a housing, the post extending from aninternal surface of the second side towards the first side, the post,the outer wall and the second side defining a trench, the channel havinga first end and a second end and being located between an internalsurface of the first side and an upper surface of the post, the channeldefining a gap between the first and second plates, the first reservoirbeing coupled to the first end of the channel and containing a thermallyconductive liquid, the second reservoir coupled to the second end of thechannel and containing a gas, the actuator coupled to the firstreservoir and the first end of the channel, the membrane positionedbetween the actuator and the first end of the channel and being locatedwithin the trench, the membrane having a first position and a secondposition associated with the first and second states of the actuator,respectively, the membrane being moveable between the first and secondpositions in response to the actuator being switched from the firststate to the second state, wherein the thermally conductive liquid ispushed into the gap from the first reservoir and the gas is pushed fromthe gap to the second reservoir as the membrane is moved from the firstposition to the second position, wherein the thermally conductive liquidflows from the gap to the first reservoir and the gas in the secondreservoir flows into the gap in response to the membrane being movedfrom the second position to the first position;

switching the actuator from the second state to the first state to pushthe thermally conductive liquid into the gap from the first reservoir,wherein the gas is pushed from the gap to the second reservoir as themembrane is moved from the second position to the first position; and

switching the actuator from the first state to the second state to allowthe thermally conductive liquid to flow from the gap to the firstreservoir, wherein the gas in the second reservoir flows into the gap inresponse to the membrane being moved from the first position to thesecond position.

Oxygen Seal Clauses

1. A seal for use with a device having a housing forming an internalcavity, the housing having an interface that connects the internalcavity to an external environment, comprising:

a sealing component located within the housing and being coupled to theinterface and being configured to restrict entry of a gas from theexternal environment to the internal cavity; and,

an absorbing component located within the housing between the sealingcomponent and the internal cavity and configured to absorb any gas thatpasses the sealing component.

2. A seal, as set forth in clause 1, wherein the device is a thermaldevice and the housing is formed from a first plate and a second plate,wherein the first plate may operate at a higher temperature than thesecond plate.

3. A seal, as set forth in clause 2, wherein the thermal device is athermal switch.

4. A seal, as set forth in clause 2, wherein the interface is formed bya seam between the first and second plates.

5. A seal, as set forth in clause 4, wherein the sealing componentincludes a first cavity within the housing, wherein the first cavity iscoupled to the interface.

6. A seal, as set forth in clause 1, wherein the first cavity contains agas blocking material.

7. A seal, as set forth in clause 6, wherein the gas blocking materialis grease.

8. A seal, as set forth in clause 6, wherein the gas blocking materialis vacuum grease.

9. A seal, as set forth in clause 6, wherein the absorbing componentincludes a second cavity within the housing, wherein the second cavityis coupled to the interface.

10. A seal, as set forth in clause 9, wherein the second cavity containsa gas absorbing material.

11. A seal, as set forth in clause 10, wherein the sealing componentincludes an isolating element extending from one of the first and secondplates into the first cavity forming a gap between the isolating elementand another one of the first and second plates.

12. A seal, as set forth in clause 11, wherein the isolating elementincludes a fin extending from the one of the first and second plates anda flange connected to the fin, the gap being between the flange and theother one of the first and second plates.

13. A seal, as set forth in clause 9 wherein the first and secondcavities are respective ring-shaped trenches that surround the internalcavity.

14. A seal, as set forth in clause 1, wherein the gas is oxygen.

15. A seal, as set forth in clause 1, further including a cavity withinthe housing, wherein the cavity is coupled to the interface andsurrounds the internal cavity, wherein the sealing component includes agas blocking material within the cavity and the absorbing componentincludes a gas absorbing material within the cavity.

16. A seal, as set forth in clause 15, wherein the gas blocking materialis a grease and the gas absorbing material is mixed with the grease.

17. A seal, as set forth in clause 15, wherein the cavity is aring-shaped trench that surrounds the internal cavity.

18. A seal for use with a thermal device having first and second platesforming a housing, the housing forming an internal cavity, the housinghaving an interface that connects the internal cavity to an externalenvironment, the interface being formed by a seam between the first andsecond plates, comprising:

a sealing component located within the housing and being coupled to theinterface and being configured to restrict entry of a gas from theexternal environment to the internal cavity, the sealing componentincluding a first cavity within the housing and an isolating element,wherein the first cavity is coupled to the interface and surrounds theinternal cavity, the first cavity containing a gas blocking material,the isolating element extending from one of the first and second platesinto the first cavity forming a gap between the isolating element andanother one of the first and second plates.

19. A seal, as set forth in clause 18, the seal further comprising:

an absorbing component located within the housing between the sealingcomponent and the internal cavity and configured to absorb any gas thatpasses the sealing component, the absorbing component including a secondcavity within the housing, the second cavity being coupled to theinterface and surrounding the internal cavity.

20. A seal, as set forth in clause 19, wherein the first and secondcavities are respective ring-shaped trenches that surround the internalcavity.

21. A seal, as set forth in clause 18, wherein the thermal device is athermal switch.

22. A seal, as set forth in clause 18, wherein the gas blocking materialis grease.

23. A seal, as set forth in clause 18, wherein the gas blocking materialis vacuum grease.

24. A seal, as set forth in clause 19, wherein second trench contains agas absorbing material.

25. A seal, as set forth in clause 16, wherein the gas is oxygen.

26. A seal, as set forth in clause 16, wherein the isolating elementincludes a fin extending from the one of the first and second plates anda flange connected to the fin, the gap being between the flange and theother one of the first and second plates.

27. A thermal device, comprising:

a first plate;

a second plate coupled to the first plate forming a housing, the housingforming an internal cavity, the housing having an interface thatconnects the internal cavity to an external environment, the interfacebeing formed by a seam between the first and second plates;

a sealing component located within the housing and being coupled to theinterface and being configured to restrict entry of a gas from theexternal environment to the internal cavity; and,

an absorbing component located within the housing between the sealingcomponent and the internal cavity and configured to absorb any gas thatpasses the sealing component.

28. A thermal device, comprising:

a first plate;

a second plate coupled to the first plate forming a housing, the housingforming an internal cavity, the housing having an interface thatconnects the internal cavity to an external environment, the interfacebeing formed by a seam between the first and second plates, the seamtraversing an outer perimeter of the housing;

a sealing component located within the housing and being coupled to theinterface and being configured to restrict entry of a gas from theexternal environment to the internal cavity, the sealing componentincluding a first trench within the housing and an isolating element,wherein the first trench is coupled to the interface and surrounds theinternal cavity, the first trench containing a gas blocking material,the isolating element extending from the one of the first and secondplates into the first trench forming a gap between the isolating elementand the other one of the first and second plates; and,

an absorbing component located within the housing between the sealingcomponent and the internal cavity and configured to absorb any gas thatpasses the sealing component, the absorbing component including a secondtrench within the housing, the second trench being coupled to theinterface and surrounding the internal cavity.

Thermal Device Clauses

1. A thermal device for controlling a temperature associated with acontrolled component, comprising:

a thermal switch having an on-state and an off-state; and,

a heat sink, the thermal switch further including:

a first plate being composed from a thermally conductive material andbeing thermally coupled to the controlled component;

a second plate being composed from a thermally conductive material, thefirst and second plates being connected to form an internal cavityhaving a channel defining a gap between the first and second plate, theheat sink being coupled to the second plate;

a first reservoir coupled to the channel, the first reservoir containinga thermally conductive liquid; and,

an actuator coupled to the first reservoir and the channel, the actuatorbeing moveable between a first state and a second state corresponding tothe on-state and the off-state of the thermal switch, respectively, andbeing configured to allow the thermally conductive liquid to flow fromthe reservoir to the channel when the actuator is in the first state andto allow the thermally conductive liquid to flow from the channel to thefirst reservoir when the actuator is in the second state.

2. A thermal device, as set forth in clause 1, wherein the heat sink isan external heat sink fastened to an external surface of the secondplate.

3. A thermal device, as set forth in clause 2, wherein the heat sink isair cooled.

4. A thermal device, as set forth in clause 2, wherein the heat sink isliquid cooled.

5. A thermal device, as set forth in clause 1, wherein the controlledcomponent is a thermoelectric cooler connected an external surface ofthe first plate.

6. A thermal device, as set forth in clause 1, wherein the controlledcomponent is a heat source.

7. A thermal device, as set forth in clause 6, wherein the controlledcomponent is a heat pipe.

8. A thermal device, as set forth in clause 1, wherein the controlledcomponent is a liquid-based thermal coupling device.

9. A thermal device, as set forth in clause 1, wherein the heat sinkincludes one or more cooling channels embedded in the second plate.

10. A thermal device, as set forth in clause 1, wherein the controlledcomponent is a heat generating component.

11. A thermal device, as set forth in clause 1, further comprising aheating device coupled between the first plate and the controlledcomponent.

12. A thermal device as set forth in clause 11, wherein the heatingdevice is one of a film heater, a strip heater and a cast heater.

13. A thermal device, as set forth in clause 1, further comprising afirst liquid based coupling device coupled to the first plate, whereinthe heat sink includes a second liquid based coupling device coupled tothe second plate, the first and second liquid based coupling devices andthe thermal switch forming a variable liquid-liquid heat exchanger.

14. A thermal device, comprising:

a thermoelectric cooler;

a thermal switch having an on-state and an off-state; and,

a heat sink, the thermal switch further including:

a first plate being composed from a thermally conductive material andbeing thermally coupled to the thermoelectric cooler;

a second plate being composed from a thermally conductive material, thefirst and second plates being connected to form an internal cavityhaving a channel defining a gap between the first and second plate andbeing coupled to the heat sink;

a first reservoir coupled to the channel, the first reservoir containinga thermally conductive liquid; and,

an actuator coupled to the first reservoir and the channel, the actuatorbeing moveable between a first state and a second state corresponding tothe on-state and the off-state of the thermal switch, respectively, andbeing configured to allow the thermally conductive liquid to flow fromthe reservoir to the channel when the actuator is in the first state andto allow the thermally conductive liquid to flow from the channel to thefirst reservoir when the actuator is in the second state.

15. A thermal device for controlling a temperature associated with aheat source, comprising:

a thermal switch having an on-state and an off-state; and,

a plurality of cooling channels in the second plate acting as a heatsink, the thermal switch further including:

a first plate being composed from a thermally conductive material andbeing coupled to the heat source;

a second plate being composed from a thermally conductive material, thefirst and second plates being connected to form an internal cavityhaving a channel defining a gap between the first and second plate, theplurality of cooling channels being located within the second plate andacting as a heat sink;

a first reservoir coupled to the channel, the first reservoir containinga thermally conductive liquid;

an actuator coupled to the first reservoir and the channel, the actuatorbeing moveable between a first state and a second state corresponding tothe on-state and the off-state of the thermal switch, respectively, andbeing configured to allow the thermally conductive liquid to flow fromthe reservoir to the channel when the actuator is in the first state andto allow the thermally conductive liquid to flow from the channel to thefirst reservoir when the actuator is in the second state.

16. A thermal device for controlling a temperature associated with aworkpiece, comprising:

a heating device coupled to the workpiece;

a thermal switch having an on-state and an off-state; and,

a plurality of cooling channels, the thermal switch further including:

a first plate being composed from a thermally conductive material andbeing coupled to the heating device;

a second plate being composed from a thermally conductive material, thefirst and second plates being connected to form an internal cavityhaving a channel defining a gap between the first and second plate, theplurality of cooling channels being located within the second plate andacting as a heat sink;

a first reservoir coupled to the channel, the first reservoir containinga thermally conductive liquid;

an actuator coupled to the first reservoir and the channel, the actuatorbeing moveable between a first state and a second state corresponding tothe on-state and the off-state of the thermal switch, respectively, andbeing configured to allow the thermally conductive liquid to flow fromthe reservoir to the channel when the actuator is in the first state andto allow the thermally conductive liquid to flow from the channel to thefirst reservoir when the actuator is in the second state.

17. A thermal device, as set forth in clause 16, wherein the heatingdevice is one of a film heater, a strip heater and a cast heater.

18. A thermal device, comprising:

a thermal switch having an on-state and an off-state; and,

a first liquid-based thermal coupling device, the thermal switch furtherincluding:

a first plate being composed from a thermally conductive material andbeing thermally coupled to the first liquid-based thermal couplingdevice;

a second plate being composed from a thermally conductive material, thefirst and second plates being connected to form an internal cavityhaving a channel defining a gap between the first and second plate;

a first reservoir coupled to the channel, the first reservoir containinga thermally conductive liquid; and,

an actuator coupled to the first reservoir and the channel, the actuatorbeing moveable between a first state and a second state corresponding tothe on-state and the off-state of the thermal switch, respectively, andbeing configured to allow the thermally conductive liquid to flow fromthe reservoir to the channel when the actuator is in the first state andto allow the thermally conductive liquid to flow from the channel to thefirst reservoir when the actuator is in the second state; and,

a second liquid-based thermal coupling device coupled to the secondplate, the first and second liquid-based thermal coupling devices andthe thermal switch forming a variable liquid-liquid heat exchanger.

Thermal Device with Multiple Thermal Switch Clauses

1. A thermal device for controlling a temperature associated with aworking surface, comprising:

a first plate being composed from a thermally conductive material;

a second plate being composed from a thermally conductive material, thefirst and second plates being connected to form first and secondinternal cavities, one of the first and second plates includes an outersurface that forms the working surface; and

a thermal switch located in each internal cavity, each thermal switchhaving an on-state and an off-state, wherein at least one of theswitches includes:

a channel in the respective internal cavity defining a gap between thefirst and second plates,

a first reservoir coupled to the channel, the first reservoir containinga thermally conductive liquid, and,

an actuator coupled to the first reservoir and the channel, the actuatorbeing moveable between a first state and a second state corresponding tothe on-state and the off-state of the thermal switch, respectively, andbeing configured to allow the thermally conductive liquid to flow fromthe reservoir to the channel when the actuator is in the first state andto allow the thermally conductive liquid to flow from the channel to thefirst reservoir when the actuator is in the second state.

2. A thermal device, as set forth in clause 1, further comprising aheating element embedded in the first plate.

3. A thermal switch, as set forth in clause 1, wherein the firstreservoir and the channel of the at least one of the switches are partof a closed system, wherein the thermally conductive liquid is pushedinto the channel from the first reservoir as the actuator is moved fromthe second state to the first state.

4. A thermal device, as set forth in clause 3, wherein the channel has afirst end and a second end, the actuator being coupled to the first endof the channel, further comprising a second reservoir coupled to thesecond end of the channel, the second reservoir containing a gas.

5. A thermal device, as set forth in clause 4, wherein each switchfurther comprises a gas entry/exit point between the second reservoirand the channel, wherein a height of the entry/exit point is less than aheight of the gap.

6. A thermal device, as set forth in clause 1, wherein the at least oneof the switches further comprises a membrane positioned between theactuator and the channel and having a first position and a secondposition associated with the first and second states of the actuator,respectively, the membrane being moveable between the first and secondpositions in response to the actuator being switched from the firststate to the second state.

7. A thermal device, as set forth in clause 6, wherein the firstreservoir, the second reservoir and the channel form part of a closedsystem, wherein the thermally conductive liquid is pushed into thechannel from the first reservoir as the membrane is moved from thesecond position to the first position.

8. A thermal device, as set forth in clause 7, wherein the thermallyconductive liquid flows from the channel to the first reservoir and thegas in the second reservoir flows into the channel in response to themembrane being moved from the position to the second position.

9. A thermal device, as set forth in clause 1, wherein the thermallyconductive liquid is a liquid metal.

10. A thermal device, as set forth in clause 1, wherein the at least oneof the switches further comprises a dividing plate positioned betweenthe first and second plates and configured to divide the channel into aplurality of conduction zones, each conduction zone having at leasthaving at least one gas entry/exit point, each of the at least one gasentry/exit points configured to minimize entry of the thermallyconductive liquid into the at least one gas entry/exit point.

11. A thermal device, as set forth in clause 1, wherein the at least oneof the thermal switches is ring-shaped.

12. A thermal device, comprising:

a first plate being composed from a thermally conductive material;

a second plate being composed from a thermally conductive material, thefirst and second plates being connected by a plurality of fasteners toform first and second internal cavities, one of the first and secondplates includes an outer surface that forms the working surface; and

a thermal switch located in each internal cavity, each thermal switchhaving an on-state and an off-state and first and second sides, at leastone of the thermal switches including:

-   -   a post extending from an internal surface of the second side        towards the first side, the post and the second side defining a        trench;    -   a channel having a first end and a second end and being located        between an internal surface of the first side and an upper        surface of the post, the channel defining a gap between the        first and second plates;    -   a first reservoir coupled to the first end of the channel and        containing a thermally conductive liquid;    -   a second reservoir coupled to the second end of the channel and        containing a gas;    -   an actuator coupled to the first reservoir and the first end of        the channel; and    -   a membrane positioned between the actuator and the first end of        the channel and being located within the trench, the membrane        having a first position and a second position associated with        the first and second states of the actuator, respectively, the        membrane being moveable between the first and second positions        in response to the actuator being switched from the first state        to the second state, wherein the thermally conductive liquid is        pushed into the gap from the first reservoir and the gas is        pushed from the gap to the second reservoir as the membrane is        moved from the second position to the first position, wherein        the thermally conductive liquid flows from the gap to the first        reservoir and the gas in the second reservoir flows into the gap        in response to the membrane being moved from the first position        to the second position.

13. A thermal device, as set forth in clause 12, further comprising ashim located between the first and second plates configured to providethermal isolation therebetween.

14. A thermal device, as set forth in clause 12, wherein the fastenersare located partially in an outer wall of the second plate, the thermaldevice further comprising an oxygen seal located between the interiorsurface of the first plate and an upper surface of the outer wall andadjacent the fasteners opposite the outer wall.

15. A thermal device, comprising:

a first plate being composed from a thermally conductive material;

a second plate being composed from a thermally conductive material, thefirst and second plates being connected by a plurality of fasteners toform first and second internal cavities, one of the first and secondplates includes an outer surface that forms the working surface;

a shim located between the first and second plates configured to providethermal isolation therebetween;

an oxygen seal located between the interior surface of the first plateand an upper surface of an outer wall and adjacent the fasteners; and

a thermal switch located in each internal cavity, each thermal switchhaving an on-state and an off-state and first and second sides, at leastone of the thermal switches including:

-   -   a post extending from an internal surface of the second side        towards the first side, the post, outer wall and second side        defining a trench;    -   a channel having a first end and a second end and being located        between an internal surface of the first plate and an upper        surface of the post, the channel defining a gap between the        first and second plates;    -   a gas entry/exit point located between the interior surface of        the first plate and an upper surface of the post, wherein a        height of the gas entry/exit point is less than a height of the        gap,    -   a first reservoir coupled to the first end of the channel and        containing a thermally conductive liquid;    -   a second reservoir coupled to the second end of the channel and        containing a gas;    -   a dividing plate positioned between the first and second plates        and configured to divide the channel into a plurality of        conduction zones;    -   an actuator coupled to the first reservoir and the first end of        the channel, the actuator being located within the trench and        surrounding the post;    -   a membrane positioned between the actuator and the first end of        the channel and being located within the trench, the membrane        having a first position and a second position associated with        the first and second states of the actuator, respectively, the        membrane being moveable between the first and second positions        in response to the actuator being switched from the first state        to the second state, wherein the thermally conductive liquid is        pushed into the gap from the first reservoir as the membrane is        moved from the second position to the first position, wherein        the thermally conductive liquid flows from the gap to the first        reservoir and the gas in the second reservoir flows into the gap        in response to the membrane being moved from the first position        to the second position.

16. A thermal device, as set forth in clause 15, wherein the trenchextends around a periphery of the second plate and surrounds the post,wherein the actuator is located within the trench.

17. A thermal device, as set forth in clause 16, wherein the actuatorincludes an electric solenoid having a solenoid coil and a circularplunger, wherein the solenoid coil surrounds and is concentric with thepost, the circular plunger being located adjacent, and being concentricwith, the solenoid coil.

18. A thermal switch, as set forth in clause 16, wherein the actuator isa pneumatic actuator including a plunger, a bellows coupled to theplunger and to a source of pressurized air.

19. A thermal device having, comprising:

a first plate being composed from a thermally conductive material;

a second plate being composed from a thermally conductive material, thefirst and second plates being connected by a plurality of fasteners toform first and second internal cavities, one of the first and secondplates includes an outer surface that forms the working surface, whereinthe first side, the second side and the outer wall surround the internalcavities and form a housing, wherein the fasteners are located partiallyin the outer wall of the second plate;

a shim located between the first and second plates configured to providethermal isolation therebetween;

an oxygen seal located between the interior surface of the first plateand an upper surface of the outer wall and adjacent the fasteners;

a thermal switch located in each internal cavity, each thermal switchhaving an on-state and an off-state and first and second sides, at leastone of the thermal switches including:

a post extending from an internal surface of the second side towards thefirst side, the post, outer wall and second side defining a trench, thetrench being located within a central area of the thermal switch, thepost surrounding the trench;

a channel having a first end and a second end and being located betweenan internal surface of the first plate and an upper surface of the post,the channel defining a gap between the first and second plates;

a gas entry/exit point located between the interior surface of the firstplate and an upper surface of the post, wherein a height of the gasentry/exit point is less than a height of the gap,

a first reservoir coupled to the first end of the channel and containinga thermally conductive liquid;

a second reservoir coupled to the second end of the channel andcontaining a gas;

a dividing plate positioned between the first and second plates andconfigured to divide the channel into a plurality of conduction zones;

an actuator coupled to the first reservoir and the first end of thechannel, the actuator being located within the trench;

a membrane positioned between the actuator and the first end of thechannel and being located within the trench, the membrane having a firstposition and a second position associated with the first and secondstates of the actuator, respectively, the membrane being moveablebetween the first and second positions in response to the actuator beingswitched from the first state to the second state, wherein the thermallyconductive liquid is pushed into the gap from the first reservoir as themembrane is moved from the second position to the first position,wherein the thermally conductive liquid flows from the gap to the firstreservoir and the gas in the second reservoir flows into the gap inresponse to the membrane being moved from the first position to thesecond position.

Thermal Switch with Pneumatic Actuator Clauses

1. A thermal switch, comprising:

a first plate being composed from a thermally conductive material;

a second plate being composed from a thermally conductive material, thefirst and second plates being connected to form an internal cavityhaving a channel defining a gap between the first and second plate;

a first reservoir coupled to the channel, the first reservoir containinga thermally conductive liquid; and,

a pneumatic actuator coupled to the first reservoir and the channel, thepneumatic actuator being moveable between a first state and a secondstate corresponding to the on-state and the off-state of the thermalswitch, respectively, and being configured to allow the thermallyconductive liquid to flow from the first reservoir to the channel whenthe pneumatic actuator is in the first state and to allow the thermallyconductive liquid to flow from the channel to the first reservoir whenthe actuator is in the second state.

2. A thermal switch, as set forth in clause 1, wherein the pneumaticactuator includes a source of pressurized air, a bellows, and plunger,the source of pressurized air controllably coupled to the bellows, theplunger being coupled to the bellows and being moveable between firstand second positions corresponding to the first and second states of thepneumatic actuators respectively.

3. A thermal switch, as set forth in clause 2, wherein the bellows actson the plunger to move the plunger from the first position to the secondplunger when pressurized air from the source of pressurized air isapplied to the bellows.

4. A thermal switch, as set forth in clause 3, further comprising areturn spring coupled to the bellows and being configured to move theplunger from the second position to the first position when the sourceof pressurized air is removed from the bellows.

5. A thermal switch, as set forth in clause 1, wherein the firstreservoir and the channel form part of a closed system, wherein thethermally conductive liquid is pushed into the channel from the firstreservoir as the pneumatic actuator is moved from the second state tothe first state.

6. A thermal switch, as set forth in clause 1, wherein the channel has afirst end and a second end, the pneumatic actuator being coupled to thefirst end of the channel, further comprising a second reservoir coupledto the second end of the channel, the second reservoir containing a gas.

7. A thermal switch, as set forth in clause 6, further comprising a gasentry/exit point between the second reservoir and the channel, wherein aheight of the entry/exit point is less than a height of the gap.

8. A thermal switch, as set forth in clause 6, further comprising amembrane positioned between the pneumatic actuator and the channel andhaving a first position and a second position associated with the firstand second states of the actuator, respectively, the membrane beingmoveable between the first and second positions in response to thepneumatic actuator being switched from the first state to the secondstate.

9. A thermal switch, as set forth in clause 8, wherein the firstreservoir, the second reservoir and the channel form part of a closedsystem, wherein the thermally conductive liquid is pushed into thechannel from the first reservoir as the membrane is moved from thesecond position to the first position.

10. A thermal switch, as set forth in clause 9, wherein the thermallyconductive liquid flows from the channel to the first reservoir and thegas in the second reservoir flows into the channel in response to themembrane being moved from the position to the second position.

11. A thermal switch, as set forth in clause 1, wherein the gap definesat least one conduction zone within the channel.

12. A thermal switch, as set forth in clause 10, wherein the at leastone conduction zone has a length of less than or equal to 0.5 inches.

13. A thermal switch, as set forth in clause 10, wherein the at leastone conduction zone has a length of less than or equal to 0.2 inches.

14. A thermal switch, as set forth in clause 10, wherein the at leastone conduction zone has a length of less than or equal to 0.1 inches.

15. A thermal switch, as set forth in clause 10, wherein the at leastone conduction zone has a width of less than 1 inch.

16. A thermal switch, as set forth in clause 1, wherein the gap has aheight of less than or equal to 0.2 inches.

17. A thermal switch, as set forth in clause 1, wherein the gap has aheight of less than or equal to 0.1 inches.

18. A thermal switch, as set forth in clause 1, wherein the gap has aheight of less than or equal to 0.02 inches.

19. A thermal switch as set forth in clause 1, further comprising adividing plate positioned between the first and second plates andconfigured to divide the channel into a plurality of conduction zones,each conduction zone having at least one gas entry/exit point, each ofthe at least one gas entry/exit points configured to minimize entry ofthe thermally conductive liquid into the at least one gas entry/exitpoint.

20. A thermal switch, as set forth in clause 1, wherein the thermallyconductive liquid is a liquid metal.

21. A thermal switch, comprising:

a first plate being composed from a thermally conductive material;

a second plate being composed from a thermally conductive material, thefirst and second plates being connected to form an internal cavityhaving a channel forming a gap between the first and second plates, thechannel having a first end and a second end;

a dividing plate positioned between the first and second plates andbeing configured to divide the channel into a plurality of conductionzones, each conduction zone having at least one gas entry/exit point;

a first reservoir coupled to the first end of the channel, the firstreservoir containing a liquid metal;

a second reservoir coupled to the channel, the second reservoircontaining a gas;

a pneumatic actuator coupled to the first reservoir and the first end ofthe channel, the actuator being moveable between first and secondstates, the first reservoir, second reservoir and the channel formingpart of a closed system; and,

a membrane positioned between the actuator and the channel and having afirst position and a second position associated with the first andsecond states of the pneumatic actuator, respectively, the membranebeing moveable between the first and second positions in response to thepneumatic actuator being switched from the first state to the secondstate, wherein the liquid metal is pushed into the conduction zones fromthe first reservoir as the membrane is moved from the second position tothe first position, wherein the liquid metal flows from the conductionzones to the first reservoir and the gas in the second reservoir flowsinto the conduction zones in response to the membrane being moved fromthe first position to the second position.

Semiconductor Manufacturing/Testing Related Clauses

1. A process module, comprising:

a processing chamber for receiving a semiconductor wafer; and,

a thermal switch coupled to the processing chamber, the thermal switchincluding:

a first plate being composed from a thermally conductive material;

a second plate being composed from a thermally conductive material, thefirst and second plates being connected to form an internal cavityhaving a channel defining a gap between the first and second plate;

a first reservoir coupled to the channel, the first reservoir containinga thermally conductive liquid; and,

an actuator coupled to the first reservoir and the channel, the actuatorbeing moveable between a first state and a second state corresponding tothe on-state and the off-state of the thermal switch, respectively, andbeing configured to allow the thermally conductive liquid to flow fromthe first reservoir to the channel when the actuator is in the firststate and to allow the thermally conductive liquid to flow from thechannel to the first reservoir when the actuator is in the second state.

2. A process module, as set forth in clause 1, wherein the semiconductorwafer is a silicon wafer.

3. A process module, as set forth in clause 1, wherein the temperatureof the semiconductor wafer is controlled during a testing ormanufacturing process.

4. A process module, as set forth clause 3, wherein the process moduleincludes a heat source for heating the semiconductor wafer.

5. A process module, as set forth in clause 4, wherein the heat sourceis one or more of a plasma, radiant heater, heat pipe, film heater,strip heater, cast heater, hot gas or liquid, laser, exothermic chemicalreaction and other suitable source.

6. A process module, as set forth in clause 4, wherein the thermalswitch is configured as a cooling plate.

7. A process module, as set forth in clause 6, further comprising a heatsink coupled to the second plate.

8. A process module, as set forth in clause 7, wherein the heat sinkincludes one or more cooling channels.

9. A process module, as set forth in clause 7, wherein the heat sink isintegrally formed in the second plate.

10. A process module, as set forth in clause 7, wherein the heat sink isthermally coupled to the second plate.

11. A process module, as set forth in clause 6, wherein the heat sourceis embedded within the first plate.

12. A process module, as set forth in clause 11, further including a topelectrode assembly coupled to the first plate, wherein the thermalswitch is thermally coupled to the top electrode assembly.

13. A process module, as set forth in clause 6, further comprising aceramic plate coupled to the first plate.

14. A process module, as set forth in clause 13, wherein the heat sourceis embedded in the ceramic plate.

15. A process module, as set forth in clause 13, wherein the heat sourceis between the first plate and the ceramic plate.

16. An inductively coupled plasma process module, comprising:

a processing chamber for receiving a semiconductor wafer and having avessel and a ceramic component, the vessel and the ceramic componentforming an internal plasma cavity; and,

a retention device located within the internal plasma cavity andconfigured to support and/or hold the semiconductor wafer in place, theretention device including a retention device temperature controlassembly having a thermal switch coupled to the processing chamber, thethermal switch including:

a first plate composed from a thermally conductive material;

a second plate being composed from a thermally conductive material, thefirst and second plates being connected to form an internal cavityhaving a channel defining a gap between the first and second plate;

a first reservoir coupled to the channel, the first reservoir containinga thermally conductive liquid; and,

an actuator coupled to the first reservoir and the channel, the actuatorbeing moveable between a first state and a second state corresponding tothe on-state and the off-state of the thermal switch, respectively, andbeing configured to allow the thermally conductive liquid to flow fromthe first reservoir to the channel when the actuator is in the firststate and to allow the thermally conductive liquid to flow from thechannel to the first reservoir when the actuator is in the second state.

17. An inductively coupled plasma process module, as set forth in clause16, including a junction between the vessel and the ceramic component,wherein the thermal switch is coupled to the junction.

18. An inductively coupled plasma process module, as set forth in clause16, wherein the retention device is an electrostatic chuck (ESC).

19. An inductively coupled plasma process module, as set forth in clause16, wherein the retention device is a vacuum chuck.

20. An inductively coupled plasma process module, as set forth in clause16, wherein the retention device includes a wafer support.

21. A capacitively coupled plasma process module, comprising:

a processing chamber having an internal plasma cavity and configured toreceive a semiconductor wafer; and,

a top electrode located within the internal plasma cavity and having atop electrode temperature control assembly;

a retention device located within the internal plasma cavity and beingconfigured to hold and/or support the semiconductor wafer in place, theretention device including a retention device temperature controlassembly, at least one of the top electrode temperature control assemblyand the retention device temperature control assembly including athermal switch, each of the of the thermal switches including:

-   -   a first plate composed from a thermally conductive material;    -   a second plate being composed from a thermally conductive        material, the first and second plates being connected to form an        internal cavity having a channel defining a gap between the        first and second plate;    -   a first reservoir coupled to the channel, the first reservoir        containing a thermally conductive liquid; and,    -   an actuator coupled to the first reservoir and the channel, the        actuator being moveable between a first state and a second state        corresponding to the on-state and the off-state of the thermal        switch, respectively, and being configured to allow the        thermally conductive liquid to flow from the first reservoir to        the channel when the actuator is in the first state and to allow        the thermally conductive liquid to flow from the channel to the        first reservoir when the actuator is in the second state.        Thermal Switch with Passive Actuator Clauses

1. A thermal switch having an on-state and an off-state, comprising:

a first plate being composed from a thermally conductive material;

a second plate being composed from a thermally conductive material, thefirst and second plates being connected to form an interior cavityhaving a channel defining a gap between the first and second plate;

a first reservoir coupled to the channel, the first reservoir containinga thermally conductive liquid;

an actuation reservoir containing an actuating material; and,

a membrane connected to the first and/or second plate and separating thefirst reservoir and actuating reservoir, the membrane being moveablebetween a first state and a second state corresponding to the on-stateand the off-state of the thermal switch, respectively, wherein theactuating material expands when heated and expansion of the actuatingmaterial causes the membrane to move from the first state to the secondstate, wherein the thermally conductive liquid flows from the firstreservoir to the channel when the actuator is in the first state and tothe thermally conductive liquid flows from the channel to the firstreservoir when the actuator is in the second state.

2. A thermal switch, as set forth in clause 1, wherein the channel has afirst end and a second end, the first reservoir being coupled to thefirst end of the channel, further comprising a second reservoir coupledto the second end of the channel, the second reservoir containing a gas.

3. A thermal switch, as set forth in clause 2, further comprising a gasentry/exit point between the second reservoir and the channel, wherein aheight of the entry/exit point is less than a height of the gap.

4. A thermal switch, as set forth in clause 1, wherein the thermallyconductive liquid is a liquid metal.

5. A thermal switch, as set forth in clause 4, wherein the liquid metalis mercury.

6. A thermal switch, as set forth in clause 1, wherein the liquid metalis an alloy composed of gallium, indium and tin.

7. A thermal switch, as set forth in clause 1, wherein the actuatingmaterial is a hydrocarbon grease.

8. A thermal switch, as set forth in clause 1, wherein the actuatingmaterial is a paraffin wax.

9. A thermal switch, as set forth in clause 1, wherein the first andsecond plates form a housing, the thermal switch further including atleast one oxygen seal located between the first and second plates.

10. A thermal switch, comprising:

a first plate being composed from a thermally conductive material;

a second plate being composed from a thermally conductive material, thefirst and second plates being connected to form an internal cavityhaving a channel forming a gap between the first and second plates, thechannel having a first end and a second end;

a dividing plate positioned between the first and second plates andbeing configured to divide the channel into a plurality of conductionzones, each conduction zone having at least one gas entry/exit point;

a first reservoir coupled to the first end of the channel, the firstreservoir containing a liquid metal;

a second reservoir coupled to the channel, the second reservoircontaining a gas;

a passive actuator coupled to the first reservoir and the first end ofthe channel, the passive actuator being moveable between first andsecond states, the first reservoir, second reservoir and the channelforming part of a closed system; and,

a membrane positioned between the actuator and the channel and having afirst position and a second position associated with the first andsecond states of the passive actuator, respectively, the membrane beingmoveable between the first and second positions in response to thepassive actuator being switched from the first state to the secondstate, wherein the liquid metal is pushed into the conduction zones fromthe first reservoir as the membrane is moved from the second position tothe first position, wherein the liquid metal flows from the conductionzones to the first reservoir and the gas in the second reservoir flowsinto the conduction zones in response to the membrane being moved fromthe first position to the second position.

11. A thermal switch, as set forth in clause 10, wherein the liquidmetal is mercury.

12. A thermal switch, as set forth in clause 10, wherein the liquidmetal is an alloy composed of gallium, indium and tin.

13. A thermal switch, as set forth in clause 12, wherein the alloy is68.5% gallium, 21.5% indium and 10% tin.

14. A thermal switch, as set forth in clause 10, wherein a height of theentry/exit point is less than a height of the gap.

15. A thermal switch, as set forth in clause 10, wherein the passiveactuator includes an actuation reservoir containing an actuatingmaterial.

16. A thermal switch, as set forth in clause 10, wherein the membraneseparates the first reservoir and actuating reservoir.

17. A thermal switch, as set forth in clause 10, wherein the passiveactuator includes a bimetallic element.

18. A thermal switch, as set forth in clause 10, wherein the passiveactuator is composed from a shape memory alloy.

19. A thermal switch, as set forth in clause 10, wherein the passiveactuator is composed from a phase changing material.

20. A thermal switch, as set forth in clause 19, wherein the phasechanging material is a melting wax.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages of the present invention will be readily appreciated asthe same becomes better understood by reference to the followingdetailed description when considered in connection with the accompanyingdrawings.

FIG. 1 is a first environmental view of a thermal switch, according toan embodiment of the present invention.

FIG. 2 is a second environmental view of a thermal switch, according toan embodiment of the present invention.

FIG. 3A is a diagrammatic illustration of a thermal switch in anoff-state and having first and second plates, a first reservoir andactuator, according to a first embodiment of the present invention.

FIG. 3B is a diagrammatic illustration of the thermal switch of FIG. 3Ain an on-state.

FIG. 3C is a diagrammatic illustration of the thermal switch, in anoff-state, of FIG. 3A including an insulator between the first reservoirand the first plate.

FIG. 3D is a diagrammatic illustration of the thermal switch, in anon-state, of FIG. 3C.

FIG. 3E is a diagrammatic illustration of the thermal switch, in anoff-state, of FIG. 3A including a separate second reservoir and a gasgap, according an embodiment of the present invention.

FIG. 3F is a diagrammatic illustration of the thermal switch of FIG. 3Ein an on-state.

FIG. 3G is a diagrammatic illustration of the thermal switch, in anoff-state, of FIG. 3A including a separate second reservoir and a gasgap, according to another embodiment of the present invention.

FIG. 3H is a diagrammatic illustration of the thermal switch of FIG. 3Gin an on-state.

FIG. 3I is a diagrammatic illustration of the thermal switch, in anoff-state, of FIG. 3A including a separate second reservoir and a gasgap, according to still another embodiment of the present invention.

FIG. 3J is a diagrammatic illustration of the thermal switch of FIG. 3Iin an on-state.

FIG. 3K is a diagrammatic illustration of the thermal switch, in anoff-state, of FIG. 3A including a separate second reservoir and a gasgap, according to one more embodiment of the present invention.

FIG. 3L is a diagrammatic illustration of the thermal switch, in anoff-state, of FIG. 3A including an alternative second reservoir.

FIG. 3M is a diagrammatic illustration of a thermal switch having asloped channel, in an off-state, according to an embodiment of thepresent invention.

FIG. 3N is a diagrammatic illustration of the thermal switch of FIG. 3Min an intermediate state.

FIG. 3O is a diagrammatic illustration of the thermal switch of FIG. 3Min an on-state.

FIG. 3P is a diagrammatic illustration of a thermal switch having astepped channel, in an off-state, according to an embodiment of thepresent invention.

FIG. 3Q is a diagrammatic illustration of the thermal switch of FIG. 3Pin an intermediate state.

FIG. 3R is a diagrammatic illustration of the thermal switch of FIG. 3Pin an on-state.

FIG. 3S is a diagrammatic illustration of a thermal switch having a gapmembrane.

FIG. 3T is a diagrammatic illustration of the thermal switch of FIG. 3Sin an on-state.

FIG. 4A is a first perspective view of a thermal switch having first andsecond plates, according to a second embodiment of the presentinvention.

FIG. 4B is a first cutaway view of the first and second plates of thethermal switch of FIG. 4A.

FIG. 4C is a first cutaway view of the second plate of the thermalswitch of FIG. 4A with a single piece shim.

FIG. 4D is a second cutaway view of the second plate of the thermalswitch of Figures with a plurality of washers.

FIG. 4E is a cutaway view of the components of the thermal switch ofFIG. 4A including a membrane bonded to the second plate, according to anembodiment of the present invention.

FIG. 4F is a cutaway view of the components of the thermal switch ofFIG. 4A including a membrane and a clamp ring for connecting themembrane to the second plate.

FIG. 4G is a cutaway view of a portion of the first and second plates ofthe thermal switch of FIG. 4A, according to an embodiment of the presentinvention.

FIG. 4H is a cutaway view of a portion of the first and second plates ofthe thermal switch of FIG. 4A, according to another embodiment of thepresent invention.

FIG. 4I is a cutaway view of a portion of the first and second plates ofthe thermal switch of FIG. 4A, according to still another embodiment ofthe present invention.

FIG. 4J is a cutaway view of a portion of the first and second plates ofthe thermal switch of FIG. 4A, according to still an additionalembodiment of the present invention.

FIG. 5A is a first cutaway view of a thermal switch having first andsecond plates, according to a third embodiment of the present invention.

FIG. 5B is a second cutaway view of the first and second plates of thethermal switch of FIG. 5A.

FIG. 6A is a first perspective view of a thermal switch having first andsecond plates, according to a fourth embodiment of the presentinvention.

FIG. 6B is a top view of a first plate of the thermal switch of FIG. 6A.

FIG. 6C is side view of the thermal switch of FIG. 6A.

FIG. 6D is a top view of a second plate of the thermal switch of FIG.6A.

FIG. 6E is a perspective view of the second plate of the thermal switchof FIG. 6A.

FIG. 6F is a first cutaway view of the thermal switch of FIG. 6A.

FIG. 6G is a partial cutaway view of the thermal switch of FIG. 6A.

FIG. 6H is a second partial cutaway view of the thermal switch of FIG.6A.

FIG. 6I is an exploded cutaway view of the thermal switch of FIG. 6A.

FIG. 6J is a cutaway view of the second plate of the thermal switch ofFIG. 6A.

FIG. 6K is a top view of a dividing plate of the thermal switch of FIG.6A.

FIG. 6L is a second top view of the second plate of the thermal switchof FIG. 6A.

FIG. 6M is a perspective cutaway view of the second plate and thedividing plate of the thermal switch of FIG. 6A, with the thermal switchin an off-state.

FIG. 6N is a perspective cutaway view of the second plate and thedividing plate of the thermal switch of FIG. 6A, with the thermal switchin an on-state.

FIG. 7A is a simplified view of a seal, according to a first embodiment.

FIG. 7B is a second simplified view of the seal of FIG. 7A.

FIG. 7C is a simplified view of a seal, according to a secondembodiment.

FIG. 7D is a simplified view of a seal, according to a third embodiment.

FIG. 7E is a partial cross-sectional view of a seal, according to afourth embodiment.

FIG. 7E-1 is a partial perspective view of a second plate of the seal ofFIG. 7E.

FIG. 7F is a partial cross-sectional view of a seal, according to afifth embodiment.

FIG. 7G is a partial cross-sectional view of a seal, according to asixth embodiment.

FIG. 7H is a partial cross-sectional view of a seal, according to aseventh embodiment of.

FIG. 7I is a partial cross-sectional view of a thermal seal, accordingto an eighth embodiment.

FIG. 8 is a diagrammatic illustration of a thermal device including athermal switch, according to a first embodiment of the thermal device.

FIG. 9 is a diagrammatic illustration of a thermal device including athermal switch, according to a second embodiment of the thermal device.

FIG. 10 is a diagrammatic illustration of a thermal device including athermal switch, according to a third embodiment of the thermal device.

FIG. 11 is a diagrammatic illustration of a thermal device including athermal switch, according to a fourth embodiment of the thermal device.

FIG. 12 is a diagrammatic illustration of a thermal device including athermal switch, according to a fifth embodiment of the thermal device.

FIG. 13A is a diagrammatic illustration of a process module including athermal switch, according to a first embodiment.

FIG. 13B is a diagrammatic illustration of a process module including athermal switch, according to a second embodiment.

FIG. 13C is a diagrammatic illustration of a process module including athermal switch, according to a third embodiment.

FIG. 13D is a diagrammatic illustration of a process module including athermal switch, according to a fourth embodiment.

FIG. 13E is a diagrammatic illustration of a process module including athermal switch, according to a fifth embodiment.

FIG. 13F is a diagrammatic illustration of a process module including athermal switch, according to a sixth embodiment.

FIG. 13G is a diagrammatic illustration of a process module including athermal switch, according to a seventh embodiment.

FIG. 13H is a diagrammatic illustration of a processing chamber of aninductively coupled plasma etch process module, according to an eighthembodiment.

FIG. 13I is a diagrammatic illustration of a processing chamber of aninductively coupled plasma etch process module, according to a ninthembodiment.

FIG. 13J is a diagrammatic illustration of a processing chamber of acapacitively coupled plasma etch process module, according to a tenthembodiment.

FIG. 14A is a diagrammatic illustration of a thermal device withmultiple thermal switches, according to a first embodiment.

FIG. 14B is a diagrammatic illustration of a thermal device withmultiple thermal switches, according to a second embodiment.

FIG. 14C is a cutaway perspective view of a second plate of the thermaldevice of FIG. 14C.

FIG. 15A is a diagrammatic illustration of a thermal switch with apneumatic actuator in an off-state, according to an embodiment of thepresent invention.

FIG. 15B is a diagrammatic illustration of the thermal switch of FIG.15A in the on-state.

FIG. 16A is a cross-sectional view of a top electrode temperaturecontrol assembly with thermal switches, according to an embodiment ofthe present invention.

FIG. 16B is a first enlarged view of a thermal switch of the topelectrode temperature control assembly of FIG. 16A;

FIG. 16C is a second enlarged view of the thermal switch of FIG. 16B inan off-state.

FIG. 16D is a third enlarged view of the thermal switch of FIG. 16B inan on-state.

FIG. 16E is an exploded view of the top electrode temperature controlassembly of FIG. 16A.

FIG. 16F is a second cutaway perspective view of the top electrodetemperature control assembly of FIG. 16A.

FIG. 17A is a cross-sectional view of an exemplary electrostatic chuck.

FIG. 17B is an enlarged portion of the cutaway perspective view of FIG.17A.

FIG. 17C is a cross-section view of an electrostatic chuck temperaturecontrol assembly having a plurality of thermal switches, according to anembodiment of the present invention.

FIG. 17D is a first partial cutaway view of one of the switches of theelectrostatic chuck temperature control assembly of FIG. 17C.

FIG. 17E is a second partial cutaway view of one of the switches of theelectrostatic chuck temperature control assembly of FIG. 17C, in anoff-state.

FIG. 17F is a third cutaway view of the switch of FIG. 17E, in anon-state.

FIG. 17G is an exploded view of the electrostatic chuck temperaturecontrol assembly of FIG. 17C.

FIG. 17H is a cutaway view of the electrostatic chuck temperaturecontrol assembly of FIG. 17C.

FIG. 17I is a cutaway view of a temperature control assembly configuredwith a liquid metal thermal interface.

FIG. 17J is a cutaway view of the temperature control assembly of FIG.17I.

FIG. 18A is a first perspective view of a passively actuated thermalswitch having first and second plates, according to an embodiment of thepresent invention.

FIG. 18B is a top view of a first plate of the thermal switch of FIG.18A.

FIG. 18C is a bottom view of the thermal switch of FIG. 18A.

FIG. 18D is a first cross-sectional view of the thermal switch of FIG.18A.

FIG. 18E is a second cross-sectional view of the thermal switch of FIG.18A.

FIG. 18F is an exploded view of the passively actuated thermal switch ofFIG. 18A.

FIG. 18G is a perspective view of the second plate of the thermal switchof FIG. 18A.

FIG. 18H is a third cross-sectional view of the thermal switch of FIG.18A in an off-state.

FIG. 18I is a fourth cross-sectional view of the thermal switch of FIG.18A in an on-state.

DETAILED DESCRIPTION OF INVENTION

Referring to the Figures, wherein like numerals indicate like orcorresponding parts throughout the several views, a thermal switch orliquid metal switch 100 is utilized to control the thermal flux (or heatflux) between a first element 102 and a second element 104. Generally,thermal flux (also referred to as heat flux, heat flux density,heat-flow density or heat flow rate intensity) is a flow of energy perunit of area per unit of time, e.g., watts per square meter. Thermalflux has both a direction and a magnitude, and so it is a vectorquantity. In the illustration of FIG. 1, the first element 102 will havea higher temperature than the second element 104 and the thermal switch100 will be utilized to control the thermal flux from the first element102 to the second element 104 as indicated by arrow, hf. The thermalswitch 100 may be passively actuated, as shown in FIG. 1.

With reference to FIG. 2, the thermal switch 100 may require activeactuation. As shown, a controller 106 may be used to control the thermalswitch 100, and thus, the heat flux between the first and secondelements 102, 104. The controller 106 may be used for many differentpurposes, including but not limited to, controlling a temperature of thefirst and/or second elements 102,104. For example, the first element 102may be a workpiece and the controller 106 may be used to control atemperature of the workpiece 102 during a manufacturing process to aspecific or desired temperature or thermal profile. The thermal switch100 of the present invention may be scaled to work with workpiece(s) 102of different sizes as discussed or shown in more detail below. Thecontroller 106 may be configured to specifically control the thermalswitch 100, or as part of a control system (not shown) that isconfigured to control a larger system, e.g., a manufacturing process,including control of the thermal switch 100.

The thermal switch 100 may be controlled passively (see below) or may becontrolled electronically or pneumatically, and thus, the controller 106may be configured to deliver appropriate signals to the thermal switch100 (see below) based on the desired temperature or thermal profile.

First Embodiment

With reference to FIGS. 3A-3J, a thermal switch 100 according to a firstembodiment is shown. In the illustrated embodiment, the thermal switch100 includes a first plate 108, a second plate 110, a first reservoir124, and an actuator 128. The actuator 128 may be an active actuator ora passive actuator. In general, an active actuator changes state inresponse to a control signal. Examples of active actuators include, butare not limited to, electric solenoids, pneumatic actuators, electricmotors, piezoelectric actuators, MEMs actuators, electrostatic actuatorsand the like. In general, passive actuators change state based on anintrinsic thermal response of the actuator. Examples of passiveactuators include, but are not limited to, actuators based on thermalexpansion such as fluid in a piston or bellows, bimetallic elements,shape memory alloys and phase changing materials (such as melting wax ina piston). Passive actuators will generally have a fixed response (setat the time of assembly), whereas active actuators have greaterversatility. Various active and passive actuators are discussed infurther detail below.

The first plate 108 is composed from a thermally conductive material,such as aluminum. In use, the first element 102 is thermally coupled tothe first plate 108. For example, the first plate 108 may include anumber of threaded apertures (see below) and the first element 102 maybe bolted or otherwise fastened to the first plate 108. It should benoted that the first element 102 may be otherwise thermally coupled tothe first plate 108 including but not limited to via a thermallyconductive interface or material, for example, thermal grease or othersuitable means.

The second plate 110 is composed from a thermally conductive material,such as aluminum. In use the second element 104 is thermally coupled tothe second plate 110. For example, the second plate 110 may include anumber of (threaded) apertures (see below) and the second element 104may be bolted or otherwise fastened to the second plate 110. It shouldbe noted that the second element 104 may be otherwise thermally coupledto the second plate 110 including but not limited to via a thermallyconductive interface or material, for example, thermal grease or othersuitable means.

As explained in more depth below, the thermal switch 100 has anoff-state, as shown in FIG. 3A, and an on-state, as shown in FIG. 3B.Generally, the first and second plates 108, 110 are thermally isolatedwhen the thermal switch 100 is in the off-state and the first and secondplates 108, 110 are thermally coupled allowing the flow of heat fluxtherebetween when the thermal switch 100 is in the on-state. It shouldbe noted, that the thermal switch 100 may have a full on-state, i.e.,given the thermal properties and current parameters, e.g., temperature,of the thermal switch 100 and the first and second elements 102, 104, amaximum amount of heat flux passes through the thermal switch 100.However, the thermal switch 100 may have an infinite number of on-statesin between the off-state and the full on-state in which a variableamount of heat flux passes through the thermal switch 100.

The first and second plates 108, 110 are connected to form an internalcavity 112. The internal cavity 112 has a channel 114 that defines a gap120 between the first and second plates 108, 110.

The first reservoir 124 is coupled to the channel 114 and contains athermally conductive liquid 126, for example, a liquid metal. In oneembodiment of the present invention, the liquid metal is mercury. Inanother embodiment of the present invention, the liquid metal is aeutectic alloy, i.e., a mixture of metals having a melting point lowerthan that of any of its components. For example, the liquid metal may bean alloy composed of gallium, indium and tin. In a specific embodiment,the liquid metal is an alloy composed of 68.5% gallium, 21.5% indium and10% tin. In another specific embodiment, the liquid metal is an alloycomposed of 61% gallium, 25% indium, 13% tin and 1% zinc. However, itshould be noted that other thermally conductive liquid mays be usedwithout departing from the spirit of the invention.

It should be noted that such alloys, i.e., that include gallium, may becorrosive to certain types of metals, including aluminum. Thus, anycomponents of the thermal switch 100 that may be exposed to, or come incontact, with the thermally conductive liquid may have to be comprisedof a material to which the thermal liquid is non-corrosive or be coatedwith a protective material, such as a polymer or ceramic material. Inone embodiment, the internal surfaces of aluminum components in contactwith the alloy of gallium are protected by a vapor deposited titaniumnitride coating.

The actuator 128 is coupled to the first reservoir 124 and the channel114. The actuator is moveable between a first state (shown in FIG. 3Band a second state (shown in FIG. 3A) corresponding to the on-state andthe off-state of the thermal switch, respectively. As discussed in moredetail below, the actuator 128 is configured to allow the thermallyconductive liquid 126 to flow from the first reservoir 124 to thechannel 114 when the actuator 128 is in the first state and to allow thethermally conductive liquid 126 to flow from the channel 114 to thefirst reservoir 124 when the actuator 128 is in the second state.

The channel 114 has a first end 116 and a second end 118. In one aspectof the present invention, the gap 120 may be divided into one or moreconduction zones (see below). In the first embodiment, shown in FIGS.3A-3J, the gap 120 of the first embodiment has a single conduction zone.In the illustrated embodiment, a shim 162 may be located at the secondend 118 of the channel 114. The shim 162 may be composed of a plasticmaterial with a low coefficient of friction to allow relative movementbetween the first and second plates 108, 110.

As shown in FIG. 3A, when the thermal switch 100 is in the off-state,the thermally conductive liquid 126 is contained within the firstreservoir 124. When the thermal switch 100 is in the off-state and theactuator 128 is in the second state, and the gap 120 is essentiallyclear of the thermally conduction liquid 126. Thus, there is minimalheat flux between the first and second plates 108, 110 through the gap120. In other words, the first and second plates 108, 110 are thermallyisolated.

As shown in FIGS. 3C-3D, a layer of thermally insulating material orinsulator 164 may be placed between the first reservoir 124 and thefirst plate 108 to prevent or minimize a path for heat fluxtherethrough.

As shown in FIG. 3B, when the thermal switch 100 is in the on-state, thegap 120 is at least partially filled with the thermally conductiveliquid 126. Due to the thermal properties of the thermally conductiveliquid 126, energy, in the form of heat, is transferred from the firstplate 108 to the second plate 110. In other words, the first and secondplates 108, 110 are thermally coupled via the thermally conductiveliquid 126 when the thermal switch 100 is in the on-state.

In the illustrated embodiment, the first reservoir 124 and the channel114 are part of a closed system. As the actuator 128 is moved from thesecond state to the first state, the thermally conductive liquid 126 ispushed into the channel 114 from the first reservoir 124.

As stated above, after the actuator 128 is moved from the first state tothe second state, the thermal switch 100 is in the off-state. In oneembodiment, the gap 120 is configured such that the thermally conductiveliquid 126 flows from the channel 114 to the first reservoir 124 atleast in part by surface tension in the thermally conductive liquid 126.In another words, other forces may also be acting on the thermallyconductive liquid 126. In another embodiment, the gap 120 is configuredsuch that the thermally conductive liquid 126 flows from the channel 114to the first reservoir 124 primarily as a result of surface tension inthe thermally conductive liquid 126.

Surface tension is the tendency of fluid surfaces to shrink into theminimum surface area possible. At liquid-gas interfaces, surface tensionresults from the greater attraction of liquid molecules to each otherthan to the molecules in the gas. The net effect is an inward force atthe surface that causes the liquid to behave as if its surface werecovered with a stretched elastic membrane.

In the disclosed embodiments of the present invention, surface tensionwill act to force the thermally conductive liquid out of the gap 120.For the thermally conductive liquid to enter the gap 120, the radius ofcurvature (indicated by R in FIG. 3B) must be less than or equal to halfthe gap height. The pressure, P, required for the liquid to assume thiscurvature may be calculated with the Young-Laplace equation:

P=2γ/h, where γ is the surface tension of the liquid and h is the gapheight.

If the liquid pressure drops below this value (as when the actuator ismoved from the first position to the second position), a net force ofsurface tension will act to pull, or assist in pulling, the liquid fromthe gap 120.

The actuator 128 is coupled to the first end 116 of the channel 114. Asshown in FIGS. 3E-3J, the thermal switch 100 may include a secondreservoir 136 coupled to the second end 118 of the channel 114. In thesimplest embodiment, the second reservoir 136 is a portion of the secondend 118 of the channel 114. The second reservoir 136 may be filled witha gas. In one aspect of the present invention, any gas or gas mixturefree of oxygen may be used to avoid oxidation of the thermallyconductive liquid 126. Suitable gases are nitrogen or argon, or mixturescontaining nitrogen and/or argon.

As shown, in the illustrated embodiment, the thermal switch 100 mayfurther comprise a membrane or diaphragm 140 positioned between theactuator 128 and the channel 114. The membrane 140 has a first positionand a second position associated with the first and second states of theactuator 128, respectively. The membrane 140 is moved between the firstand second positions in response to the actuator 128 being switched fromthe first state to the second state. The first reservoir 124, the secondreservoir 136 and the channel 114 are part of a closed system. It shouldbe noted, that in some embodiments, the gas may be distributed to otherparts of the internal cavity 112, i.e., outside of the second reservoir136 and the channel 114. As the actuator 128 is moved from the secondstate to the first state, the membrane 140 is moved from the secondposition to the first position and the thermally conductive liquid 126is pushed into the channel 114 from the first reservoir 124. Themembrane 140 may be composed from a suitable flexible material,including, but not limited to, silicone, other elastomers, and metal.

As the actuator 128 is moved from the first state to the second state,the membrane 140 is moved from the first position to the second positionand the thermally conductive liquid 126 flows from the channel 114 tothe first reservoir 124 and gas 138 in the second reservoir 136 flowsinto the channel 114.

In the embodiments shown in FIGS. 3E-3L, the second reservoir 136 isseparate from the channel 114. In the illustrated embodiment, the gap120 (or conduction zone) has a length of l_(cz) and a height of h_(cz).In one embodiment, the length, l_(cz), of each conduction zone 122 isless than or equal to 0.5 inches. In another embodiment, the length,l_(cz), of each conduction zone 122 is less than or equal to 0.2 inches.In still another embodiment, the length, l_(cz), of each conduction zone122 is less than or equal to 0.1 inches.

In one embodiment, the height, h_(cz), of each conduction zone 122 isless than or equal to 0.2 inches. In another embodiment, the height,h_(cz), of each conduction zone 122 is less than or equal to 0.1 inches.In still another embodiment, the height, h_(cz), of each conduction zone122 is less than or equal to 0.02 inches.

As shown, in these embodiments the thermal switch 100 includes a gasentry/exit point 144 between the second reservoir 136 and the channel114. The gas entry/exit point 144 configured to minimize entry of thethermally conductive liquid 126 into the at least one gas entry/exitpoint, and thus, the second reservoir 136. For example, in oneembodiment, a height of the entry/exit point 144 (h_(gas_gap)) is lessthan a height of the gap (h_(cz)). As mentioned above, the pressurerequired to force the thermally conductive liquid 126 into a gap isinversely proportional to the height of the gap. Thus, minimizing thegap height of the gas entry/exit point may prevent the thermallyconductive liquid from entering the gas gap 166. As explained in moredetail below, the presence of the second reservoir 136 allows the liquidmetal to flow further into the channel 114 without causing a significantincrease in gas pressure within the channel 114. In these embodiments,the gas pressure in the channel 114 may not provide a significantcontribution to flow of the thermally conductive liquid 126 from the gap120 to the first reservoir 124 when the actuator 128 moves from thefirst position to the second position. Rather, the presence of thesecond reservoir 136 reduces the increase in gas pressure when thethermally conductive liquid 126 flows into the channel 114 to minimizethe actuating force required.

In one embodiment, shown in FIGS. 3E-3F, the second plate 110 includes astep 110A. In the illustrated embodiment, the gas gap 166 is formedbetween an upper surface of the step 110A and the lower surface of thefirst plate 108.

In another embodiment, shown in FIGS. 3G-3H, the gas gap 166 is formedby a gas gap (or dividing) plate 168. In the illustrated embodiment, thegas gap plate 168 is fixedly coupled to the second plate 110 but mayalternatively be fixedly coupled to the first plate 108. The gas gap 166is defined by a surface of the gas gap plate 168 and the surface of thefirst plate 108 (or in the alternate embodiment, the surface of thesecond plate 110). In one aspect of the present invention, the gas gapplate 168 may be composed from a plastic. It should be noted that thegas gap plate 168 in FIGS. 3G-3H, serves a function similar to the step110A in FIGS. 3E-3F. In some embodiments, features or components thatcould be formed as part of the first or second plates 108, 110 may bereplaced with a separate component formed from a plastic. This hasseveral benefits. First, the plastic component does not have to becoated to protect it from corrosion from the thermally conductive liquid126. Second, certain features which are located within the component,such as grooves, are more easily formed or machined in the plastic ascompared with aluminum.

In still another embodiment, shown in FIGS. 3I-3J, the gas gap 166 isformed by a gas gap plate 168 and an elastomer biasing member 170. Inthe illustrated embodiment, the elastomer biasing member 170 is locatedwithin a trench 172 in the second plate 110. The elastomer biasingmember 170 presses the gas gap plate 168 against the surface of thefirst plate 108. The seal created between the gas gap plate 168 and thefirst plate 108 is not airtight. This arrangement creates the smallestpossible gas gap 166, i.e., the smallest gas gap height, h_(gas_gap),and thus, minimizes the risk of the thermally conductive liquid 126entering the gas gap 166. In an alternative embodiment, grooves may beadded to the top surface of the gas gap plate 168.

In one more embodiment, shown in FIG. 3K, the gas gap 166 may be formedby shallow grooves (not shown) formed in a top surface of the step 110Ain the second plate 110. The elastomer biasing member 170, located in atrench 174 in the first plate 108, helps seal the top of the groovesleaving a small gas gap 166. The shallow grooves may be machined in thetop surface of the step 110A, e.g., by a laser or other means.

With reference to FIG. 3L, the second reservoir 136 is located aroundand/or adjacent the actuator 128. A gas channel 175 through the secondplate 110 connects the second reservoir 136 to second end 118 of thechannel 114.

In another embodiment, the gap 120 may have at least one sloped surface.In the prior embodiments, the gap 120 was of constant height.Consequently, the radius of curvature (and thus the force of surfacetension) remains constant as the thermally conductive liquid 126advances into the gap 120. When one or both of the surfaces of the gap120 are sloped, the height of the gap 120 and the radius of curvaturedecreases as the thermally conductive liquid 126 advances into the gap120. In the illustrated embodiment of FIGS. 3M-3O, a lower surface 120Aof the gap 120 is sloped such that the height of the gap 120 decreasesfrom the first end 116 of the channel 114 towards the second end 118 ofthe channel. Thus, the radius of curvature decreases as the thermallyconductive liquid 126 advances within the gap 120. For example, theradius of curvature of the thermally conductive liquid in FIG. 3O (R2)is less than the radius of curvature of the thermally conductive liquidin FIG. 3N (R1), and consequently the force of surface tension pullingthe thermally conductive liquid 126 from the gap 120 is higher. A gapconfiguration in which the height of the gap 120 decreases is useful inembodiments where it is desirable to minimize the risk of the thermallyconductive liquid 126 remaining within the gap 120 in the off-state (seebelow).

In another embodiment, as shown in FIGS. 3P-3R, the gap 120 may beconfigured with two or more discreet regions of differing height,indicated as h1 and h2 in FIG. 3M. This arrangement may be useful inapplications where it is desirable to create a thermal switch with adefinitive intermediary value of thermal conductivity (as illustrated bythe intermediary switch condition of FIG. 3Q). An abrupt change in gapheight creates a corresponding change in the fluid pressure required toforce the thermally conductive liquid 126 past the first intermediarycondition. The (active) actuator 120 may be appropriately configured toswitch between an off-state, the intermediary state, and the “fully on”state.

In general, the embodiments above rely on surface tension to draw thethermally conductive liquid 126 from the gap 120. In some embodiments,it may be desirable to augment or replace the force of surface tensionwith a second force driving the thermally conductive liquid 126 from thegap 120. In one embodiment, shown in FIGS. 3S-3T, a second membrane 121,or gap membrane, may be configured to separate the thermally conductiveliquid 126 from the first plate 108. In the on-state as illustrated inFIG. 3T, the stretched gap membrane 1212 applies a force to thethermally conductive liquid 126 which will tend to expel the liquid fromthe gap 120 when the actuator is moved from the first to secondposition.

Second Embodiment

With reference to FIGS. 4A-4J, a thermal switch 100 according to asecond embodiment is shown. For purposes of discussion, the samereference numbers are used to refer to elements of the second embodimentof the thermal switch 100 as using in the first embodiment, whereappropriate or otherwise noted.

In the illustrated embodiment, the thermal switch 100 of the secondembodiment includes a first plate 108, a second plate 110, a firstreservoir 124, and an actuator 128. The first plate 108 is composed froma thermally conductive material and forms a first side 148 of thethermal switch 100. For example, the first plate 108 may include aplurality of threaded apertures (not shown) and the first element 102may be bolted or otherwise fastened to the first plate 108. It should benoted that the first element 102 may be otherwise thermally coupled tothe first plate 108 including but not limited to via a thermallyconductive interface or material, for example, thermal grease or othersuitable means.

The second plate 110 is composed from a thermally conductive materialand forms a second side 150 of the thermal switch 100. The second plate110 includes a plurality of threaded apertures 176 and may be coupled tothe first plate 108 by a plurality of threaded fasteners 158. In oneembodiment, the fasteners 158 are composed from stainless steel. In theillustrated embodiment, the second side 150, an outer wall 152 extendingfrom the second side 150 and the first side 148, surround the internalcavity 112 and form the housing 146.

A post 154 extends from an internal surface of the second side 150towards the first side 148. The post 154, the outer wall 152 and bottomdefining a trench 156. A channel 114 has a first end 116 and a secondend 118. As discussed in more detail below, the channel 114 is definedbetween the first side 148 or the first plate 108 and the post 154. Theactuator 128 has a generally circular shape and surrounds the post 154.

However, in other embodiments the post 154 has a generally circularshape and surrounds the trench 156. The actuator 128 is located withinthe trench and the channel 114 is defined by the trench 156 and extendsoutward from the (center) post 154 (see below).

Returning to FIGS. 4A-4J, in the illustrated embodiment, the channel 114is defined by (and between) an internal surface of the first side 148and an upper surface of the post 154. The channel 114 defines a gap 120between the first and second plates 108, 110.

The first reservoir 124 is coupled to the first end 116 of the channel114 and contains a thermally conductive liquid 126 (not shown in FIGS.4C-4D).

In the illustrated embodiment, the first and second plates 108, 110 arethermally isolated by a shim 162. In one embodiment, shown in FIG. 4C, asingle plastic shim 162A covers at least a portion of the upper surfaceof the outer wall 152. In another embodiment, shown in FIG. 4D, aplastic washer 162B sits in each threaded aperture 176 in the secondplate 110. The shim 162 provides thermal isolation between the plates108, 110 while allowing relative movement therebetween as the firstplate 108 expands and contracts.

As shown in FIGS. 4E and 4F, the thermal switch 100 includes a membrane140 that is positioned adjacent an actuator 128. In the illustratedembodiment, the membrane 140 has a toroidal or ring shape and fitswithin the circular trench 156. An outer end or edge of the membrane 140is clamped between the first and second plates 108, 110. An adhesive mayalso be used to hold or seal the outer edge of the membrane 140 betweenthe first and second plates 108, 110 to create a seal. The inner edge ofthe membrane 140 may be bonded or affixed to the second plate 110. Inthe illustrated embodiment of FIG. 4E, the inner edge of the membrane140 is affixed to a ledge or shelf 178 positioned within the trench 156.In the embodiment as shown in FIGS. 4B-4D and 4F, the inner edge of themembrane 140 may be clamped to the second plate 110 using a clamp ring180. The clamp ring 180 may be secured by suitable means includingfasteners or adhesive (not shown).

As discussed above, the channel 114 is formed between an internalsurface of the first side 148 of the switch 100 and a surface of the(center) post 154. An enlarged view (marked by the dashed lines in FIG.4F) of one embodiment of the channel 114 is shown in FIG. 4G.

In FIG. 4G, in one embodiment of the present invention, the thermalswitch 100 may not include a second reservoir 136. The center post 154includes a central step 154A that is surrounded a toroidal orring-shaped channel 114. The channel 114 extends outwardly from thecentral step 154 from the second end 118 of the channel 114 towards thefirst end 116 of the channel 114. The first and second plates 108, 110are separated by a small gap 154B defined at an upper surface of thecentral step 154A. The small gap 154B may be considered as a secondreservoir. In the illustrated embodiment, the height of the small gap154B is much smaller than the height of the channel, h_(cz). Forexample, the height of the channel, h_(cz), may be 0.010″, while theheight of the gap 154B may be 0.002″.

As shown in FIG. 4H, a second reservoir 136 may be located within thecentral post 154. The small gap 154B serves as a gas gap (see above).The presence of the second reservoir 136 minimizes the increase in gaspressure in the channel 114 and the small gap 154B which may increasethe depth to which the thermally conductive liquid 126 travels in thechannel 114.

As shown in FIG. 4I, the small gap 154B may be created using a plasticring 182 bonded to surface of the second plate 110. The ring 182 couldalternatively be bonded to a surface of the first plate 108.Alternatively, the ring 182 could be held in position using one or morelocating pins (not shown).

In an alternative embodiment shown in FIG. 4J, a very small gap 154B maybe created using a plastic ring 182 that is pressed against the firstplate 108 (as shown) using an O-ring 184 located in a trench 186 of thesecond plate 110. One or more small channels (not shown) may be locatedin the surface of the ring 182 adjacent the first plate 108. Thechannels may be laser cut into the ring 182 and may be as small as0.0003″.

The second reservoir 136 is coupled to the second end 118 of the channel114 and contains a gas 138. The actuator 128 is coupled to the firstreservoir 124 and the first end 116 of the channel 114. The membrane 140is positioned between the actuator 128 and the first end 116 of thechannel 114 and is located within the circular trench 156. The membrane140 has a first position and a second position associated with the firstand second states of the actuator 128, respectively. The membrane 140 ismoveable between the first and second positions in response to theactuator 128 being switched from the first state to the second state.The thermally conductive liquid or liquid metal 126 is pushed into thegap 120 from the first reservoir 124 and gas 138 is pushed from the gap120 to the second reservoir 136 as the membrane 140 is moved from thesecond position to the first position. The thermally conductive liquidor liquid metal 126 flows from the gap 120 to the first reservoir 124and gas 138 in the second reservoir 136 flows into the gap 120 inresponse to the membrane 140 being moved from the first position to thesecond position.

In one aspect of the present invention, the size of the first and secondreservoirs 124, 136 are configured to control the change in pressure inthe second reservoir 136 between the on and off-states of the thermalswitch 100. In general, the volume of the second reservoir 136 is muchlarger than the displacement of the thermally conductive liquid 126, sothe increase in gas pressure in the second reservoir 136 is small. Thisreduces the actuator force required to actuate the thermal switch 100.

The first reservoir 124 is coupled to the channel 114 and contains athermally conductive liquid 126, for example, a liquid metal. In oneembodiment of the present invention, the liquid metal is mercury. Inanother embodiment of the present invention, the liquid metal is aeutectic alloy, i.e., a mixture of metals having a melting point lowerthan that of any of its components. For example, the liquid metal may bean alloy composed of gallium, indium and tin. In a specific embodiment,the liquid metal is an alloy composed of 68.5% gallium, 21.5% indium and10% tin. In another specific embodiment, the liquid metal is an alloycomposed of 61% gallium, 25% indium, 13% tin and 1% zinc. However, itshould be noted that other thermally conductive liquid may be usedwithout departing from the spirit of the invention.

The actuator 128 is coupled to the first reservoir 124 and the channel114. The actuator 128 is moveable between a first state and a secondstate corresponding to the on-state and the off-state of the thermalswitch, respectively. As discussed in more detail below, the actuator128 is configured to allow the thermally conductive liquid 126 to flowfrom the first reservoir 124 to the channel 114 when the actuator 128 isin the first state and to allow the thermally conductive liquid 126 toflow from the channel 114 to the first reservoir 124 when the actuator128 is in the second state.

The channel 114 has a first end 116 and a second end 118. In one aspectof the present invention, the gap 120 may be divided into one or moreconduction zones using a dividing plate (see below). As discussed indetail below, each conduction zone 122 has a width, w_(cz). In oneembodiment, the width of each conduction zone 122 is less than or equalto 1 inch.

In one embodiment, the height, h_(cz), of each conduction zone 122 isless than or equal to 0.2 inches. In another embodiment, the height,h_(cz), of each conduction zone 122 is less than or equal to 0.1 inches.In still another embodiment, the height, h_(cz), of each conduction zone122 is less than or equal to 0.02 inches.

The gas gap 166 includes a gas entry/exit point 144 between the secondreservoir 136 and the channel 114. The gas entry/exit point 144 isconfigured to minimize entry of the thermally conductive liquid 126 intothe at least one gas entry/exit point, and thus, the second reservoir136. For example, in one embodiment, a height of the entry/exit point144 (h_(gas_gap)) is less than a height of the gap (h_(cz)). Asexplained in more detail below, the presence of the second reservoir 136allows the liquid metal to flow further into the channel 114 withoutcausing a significant increase in gas pressure within the channel 114.

Third Embodiment

With reference to FIGS. 5A-5B, a thermal switch 100 according to a thirdembodiment is shown. For purposes of discussion, the same referencenumbers are used to refer to elements of the third embodiment of thethermal switch 100 as used in the first and second embodiments, whereappropriate or otherwise noted.

Generally, the thermal switch 100 in the third embodiment is similar tothe thermal switch 100 of the second embodiment, however, the actuator128 and first reservoir 124 are located within the center of the thermalswitch 100.

In the illustrated embodiment, the thermal switch 100 of the thirdembodiment includes a first plate 108, a second plate 110, a firstreservoir 124, and an actuator 128. The first plate 108 is composed froma thermally conductive material and forms a first side 148 of thethermal switch 100.

The second plate 110 is composed from a thermally conductive materialand forms a second side 150 of the thermal switch 100. In theillustrated embodiment, the second side 150, an outer wall 152 extendingfrom the second side 150 and the first side 148, surround the internalcavity 112 and form the housing 146.

A post 154 extends from an internal surface of the second side 150towards the first side 148. The post 154, the outer wall 152 and bottomdefining a trench 156. The post 154 has a toroidal shape and surroundsthe trench 156. The trench 156 is circular and is located in the centerof the second plate 110. The actuator 128 is located within the trench156.

A channel 114 has a first end 116 and a second end 118. As discussed inmore detail below, the channel 114 is defined between the first side 148or the first plate 108 and the post 154.

In the illustrated embodiment, the channel 114 is defined by (andbetween) an internal surface of the first side 148 and an upper surfaceof the post 154. The channel 114 defines a gap 120 between the first andsecond plates 108. 110. The first reservoir 124 is coupled to the firstend 116 of the channel 114 and contains a thermally conductive liquid126.

In the illustrated embodiment, the first and second plates 108, 110 arethermally isolated by a shim 162. As shown in FIGS. 5A and 5B, thethermal switch 100 includes a membrane 140 that is positioned adjacentthe actuator 128.

As discussed above, the channel 114 may be formed between an internalsurface of the first side 148 of the switch 100 and a surface of thetoroidal or ring-shaped post 154.

The second reservoir 136 is located within the toroidal or ring-shapedpost 154. The channel 114 extends inwardly from the post 154 towards thefirst reservoir 124. The first and second reservoirs 124, 136 areconnected by a small gap 154B or gas gap 166. In the illustratedembodiment, the height of the small gap 154 is much smaller than theheight of the channel, h_(cz). For example, the height of the channel,h_(cz), may be 0.010″, while the height of the gap 154B may be 0.002″.The gap 154B, 166 may be created between surfaces of the first andsecond plates 108, 110 or between one of the plates 108, 110 and a ring182.

The second reservoir 136 is coupled to the second end 118 of the channel114 and contains a gas 138. The actuator 128 is coupled to the firstreservoir 124 and the first end 116 of the channel 114. The membrane 140is positioned between the actuator 128 and the first end 116 of thechannel 114 and is located within the trench 156. The membrane 140 has afirst position and a second position associated with the first andsecond states of the actuator 128, respectively. The membrane 140 ismoveable between the first and second positions in response to theactuator 128 being switched from the first state to the second state.The thermally conductive liquid or liquid metal 126 is pushed into thegap 120 from the first reservoir 124 and gas 138 is pushed from the gap120 to the second reservoir 136 as the membrane 140 is moved from thesecond position to the first position. The thermally conductive liquidor liquid metal 126 flows from the gap 120 to the first reservoir 124and gas 138 in the second reservoir 136 flows into the gap 120 inresponse to the membrane 140 being moved from the first position to thesecond position.

The second plate 110 is composed from a thermally conductive material,such as aluminum. The first reservoir 124 is coupled to the channel 114and contains a thermally conductive liquid 126, for example, a liquidmetal. In one embodiment of the present invention, the liquid metal ismercury. In another embodiment of the present invention, the liquidmetal is a eutectic alloy, i.e., a mixture of metals having a meltingpoint lower than that of any of its components. For example, the liquidmetal may be an alloy composed of gallium, indium and tin. In a specificembodiment, the liquid metal is an alloy composed of 68.5% gallium,21.5% indium and 10% tin. In another specific embodiment, the liquidmetal is an alloy composed of 61% gallium, 25% indium, 13% tin and 1%zinc. However, it should be noted that other thermally conductive liquidmays be used without departing from the spirit of the invention.

The actuator 128 is coupled to the first reservoir 124 and the channel114. The actuator 128 is moveable between a first state and a secondstate corresponding to the on-state and the off-state of the thermalswitch, respectively. As discussed in more detail below, the actuator128 is configured to allow the thermally conductive liquid 126 to flowfrom the first reservoir 124 to the channel 114 when the actuator 128 isin the first state and to allow the thermally conductive liquid 126 toflow from the channel 114 to the first reservoir 124 when the actuator128 is in the second state.

The channel 114 has a first end 116 and a second end 118. In one aspectof the present invention, the gap 120 may be divided into one or moreconduction zones using a dividing plate (see below).

In one embodiment, the height, h_(cz), of each conduction zone 122 isless than or equal to 0.2 inches. In another embodiment, the height,h_(cz), of each conduction zone 122 is less than or equal to 0.1 inches.In still another embodiment, the height, h_(cz), of each conduction zone122 is less than or equal to 0.02 inches.

The gas gap 166 includes a gas entry/exit point 144 between the secondreservoir 136 and the channel 114. The gas entry/exit point 144configured to minimize entry of the thermally conductive liquid 126 intothe at least one gas entry/exit point, and thus, the second reservoir136. For example, in one embodiment, a height of the entry/exit point144 (h_(gas_gap)) is less than a height of the gap (h_(cz)). Asexplained above, the presence of the second reservoir 136 allows theliquid metal to flow further into the channel 114 without causing asignificant increase in gas pressure within the channel 114.

Fourth Embodiment

With reference to FIGS. 6A-6N, a thermal switch 100 according to afourth embodiment is shown. For purposes of discussion, the samereference numbers are used to refer to elements of the fourthembodiments as used in the first, second and/or third embodiments of thethermal switch 100, where appropriate or otherwise noted.

The thermal switch 100 of the fourth embodiment, is actuated byelectrical power via an electric solenoid (see below). The thermalswitch 100 is suitable in a general thermal control system, withcomponents bolted to either side of the thermal switch 100. A variablethermal conductivity separates the two surfaces or sides of the thermalswitch 100. The thermal conductivity is adjusted to a high or “on” stateby energizing the switch's electrical connection and changed to low or“off” state by deenergizing the electrical power. An intermediate levelof thermal conductivity may be achieved by pulsing the electrical power.

In a non-limiting example, the illustrated thermal switch 100 has aheight of 1.25″ and has a square profile with a width of 5.5″.

In the illustrated embodiment, the thermal switch 100 of the fourthembodiment includes a first plate 108, a second plate 110, a firstreservoir 124, a second reservoir 136 and an actuator 128. As discussedabove, the first reservoir 124 contains a thermally conductive liquid126, such as an alloy of gallium, indium, and tin, and the secondreservoir 136 contains a gas 138. One or more ports 125 (see FIG. 6D)may be provided to allow the first reservoir 124 to be filled with thethermally conductive liquid 126 and to allow the second reservoir 136 tobe filled with the gas 138. With respect to the thermally conductiveliquid 126, after the first reservoir 124 is filled, the port(s) may befilled with a sealing grease, followed by a press fit aluminum plug (notshown).

The first plate 108 is composed from a thermally conductive material,such as aluminum, and forms a first side 148 of the thermal switch 100.For example, the first plate 108 may include a plurality of threadedapertures 188 and the first element 102 may be bolted or otherwisefastened to the first plate 108. It should be noted that the firstelement 102 may be otherwise thermally coupled to the first plate 108including but not limited to via a thermally conductive interface ormaterial, for example, thermal grease or other suitable means.

The second plate 110 is composed from a thermally conductive material,such as aluminum, and forms a second side 150 of the thermal switch 100.The second plate 110 includes a plurality of threaded apertures 176 andmay be coupled to the first plate 108 by a plurality of threadedfasteners 158 that are threaded through threaded apertures 176 intoassociated receiving apertures (not shown) in the first plate 108. Inthe illustrated embodiment, the second side 150, an outer wall 152extending from the second side 150 and the first side 148, surround theinternal cavity 112 and form the housing 146. The second plate 110 mayalso include receiving apertures 189 to receive the fasteners (notshown) that fasten the second element 104 to the thermal switch 100.

The first reservoir 124 is coupled to the channel 114 and contains athermally conductive liquid 126, for example, a liquid metal. In oneembodiment of the present invention, the liquid metal is mercury. Inanother embodiment of the present invention, the liquid metal is aeutectic alloy, i.e., a mixture of metals having a melting point lowerthan that of any of its components. For example, the liquid metal may bean alloy composed of gallium, indium and tin. In a specific embodiment,the liquid metal is an alloy composed of 68.5% gallium, 21.5% indium and10% tin. In another specific embodiment, the liquid metal is an alloycomposed of 61% gallium, 25% indium, 13% tin and 1% zinc. However, itshould be noted that other thermally conductive liquid mays be usedwithout departing from the spirit of the invention.

With specific reference to FIGS. 6D, 6E, and 6I, the second plate 110has an outer side wall 152 and an open top that forms an internal cavity112. The first plate 108, second plate 110 and the internal cavity 112,form a housing 146 in which the remaining components of the thermalswitch 100 are located.

With reference to FIGS. 6F, 6I, and 6J, the internal cavity 112,includes a post 154 that extends from an internal surface of the secondside 150 towards the first side 148. The post 154, the outer wall 152and bottom define a trench 156. The trench 156 is generally toroidal orring-shaped and surrounds the post 154. A channel 114 has a first end116 and a second end 118. As discussed in more detail below, the channel114 is defined between the first side 148 or the first plate 108 and thepost 154. The channel 114 is defined by (and between) an internalsurface of the first side 148 and an upper surface of the post 154. Thechannel 114 defines a gap 120 between the first and second plates 108,110.

In the illustrated embodiment, the channel 114 includes a plurality ofpathways 115 formed in an upper portion 155 of the post 154, allowingthe thermally conductive liquid 126 to flow from the first reservoir 124to the conduction zones 122. The pathways 115 have a height greater thanthe height of conduction zones 122 and correspondingly lower minimumfluid pressure is required for fluid penetration. When the actuator 128and the membrane 140 move from the first state to the second state, thethermally conductive liquid 126 withdraws only from the conduction zones122 and remains in the pathways 115. The actuator 128 has a generallycircular shape and surrounds the post 154. A dividing plate 142 (seeFIGS. 6D, 6E, and 6I) is positioned between the first and second plates108, 110 and is configured to divide the channel 114 (see below) into aplurality of conduction zones 122. The dividing plate 142 defines aplurality of gas channels 175 between the second reservoir 136 and theconduction zones 122. In one embodiment of the present invention, thedividing plate 142 is composed from a plastic material, such aspolyoxymethylene and may be cut from a sheet of material using a lasercutting process.

The dividing plate 142 serves one or more of the following purposes:

-   -   dividing the channel 114 into sections (or conduction zones)        with a single flow path in and out of each respective conduction        zone 122;    -   separating the thermally conductive liquid 126 in the pathways        115 from the first plate 108 to decrease thermal conduction via        the thermally conductive liquid 126 remaining in the pathways        115 in the off-state;    -   providing a path for gas to flow out of the conduction zones        122; and,    -   providing design flexibility.

Dividing the channel 114 into smaller conduction zones 122 assists inensuring that all of the thermally conductive liquid 126 leaves or ispulled out of the channel 114 when the thermal switch 100 is in theoff-state. Embodiments employing surface tension to pull the thermallyconductive liquid 126 from the channel 114 rely on the surface of thevolume of the thermally conductive liquid 126 remaining intact. That is,if a portion of the thermally conductive liquid 126 in the gap 120separates from the bulk of the thermally conductive liquid 126 in thefirst reservoir 124, that portion will not be pulled from gap 120.Separation may be influenced by factors including adhesion between thethermally conductive liquid 126 and sides of the gap 120, a high rate ofwithdrawal, the geometry of the channels 114 and conduction zones 122,or the presence of multiple flow paths from a conduction zone 122 (thusthe need to have only a single flow path). Dividing the channel 114 intosmaller conduction zones 122 minimizes the risk of liquid separation. Inone embodiment, a maximum conduction zone length of 0.2″ was found to beeffective to ensure all of the thermally conductive liquid 126 iswithdrawn from the gap.

Further, the separate dividing plate provides design flexibility. Ifconduction zones were formed by steps in the second plate 110, then theconduction zone design would be fixed. A separate dividing plate 142provides the ability to customize the size of conduction zones prior toassembling the thermal switch 100 by changing the dividing plate ratherthan the second plate 110 which is aluminum.

Each conduction zone 122 has at least one gas entry/exit point 144located between the second reservoir 136 and the channel 114. The atleast one gas entry/exit point 144 may be located between an interiorsurface of the first plate 108 and an upper surface of the post 154. Forexample, in the illustrated embodiment (shown in FIG. 6K), the gasentry/exit points 144 are formed within the sidewalls of the gaschannels 175. The at least one gas entry/exit point 144 is configured tominimize entry of the thermally conductive liquid 126 into the at leastone gas entry/exit point 144. For example, in one aspect of the presentinvention, a height of the at least one gas entry/exit point 144 is lessthan a height of the gap 120.

Returning to 6F, which is a cross-section view of A-A from FIG. 6B, thefirst reservoir 124 is coupled to the first end 116 of the channel 114and contains a thermally conductive liquid 126. As shown, the firstreservoir 124 is generally toroidal or ring-shaped and surrounds thecenter post 154.

In the illustrated embodiment, the first and second plates 108, 110 arethermally isolated by a shim 162. In the illustrated embodiment (seeFIG. 6I), a plastic washer 162B sits in each threaded aperture 178 inthe second plate 110. Alternatively, a single plastic shim (not shown)that covers at least a portion of the upper surface of the outer wall152 may be used. The shim 162 or plastic washers 162B provide thermalisolation between the plates 108, 110 while allowing relative movementtherebetween as the first plate 108 expands and contracts.

Returning to FIG. 6F, the thermal switch 100 of the fourth embodimentmay further include an oxygen seal 190. In the illustrated embodiment,the oxygen seal 190 is located between an interior surface of the firstplate 108 and an upper surface of the outer wall 152 (adjacentfasteners. The oxygen seal 190 restricts oxygen from entering theinternal cavity 112 of the thermal switch 100 while allowing movementbetween the first and second plates 108, 110. In the illustratedembodiment, the oxygen seal 190 is positioned around the entireperimeter of the internal cavity 112 between the first and second plates108, 110. The oxygen seal 190, including several embodiments, isdescribed in further detail below. In one aspect of the presentinvention, the oxygen seal 190 keeps oxygen out of the internal cavity112 of the thermal switch 100 or minimizes the amount of oxygen that isallowed to enter the internal cavity 112 of the thermal switch 100. Inanother aspect of the present invention, the oxygen seal 190 may captureany oxygen that is within the interior 112 of the thermal switch 100.

As shown in FIGS. 6F, 6H, and 6I, the actuator 128 is coupled to thefirst reservoir 124 and a first end 116 of the channel 114. In theillustrated embodiment, the actuator 128 includes an electric solenoid192. The electric solenoid 192 includes a solenoid coil 194 in asolenoid case 196. Preferably, the solenoid coil 194 is composed fromcopper wire. The solenoid case 196 has a general circular shape and isopen on an interior side (see FIGS. 6A and 6I). The solenoid case 196and the solenoid coil 194 may be connected to the bottom of the trench186 using fasteners, adhesive or by any suitable means. In oneembodiment of the present invention, the solenoid case 196 is composedfrom stainless steel, such as 430 stainless steel.

The electric solenoid 192 further includes a circular or toroidal-shapedplunger 198. As shown on the left side of FIGS. 6F and 6H, the plunger198 includes one or more internal cavities 112 for receiving arespective bearing assembly 200. The bearing assembly 200 is mounted ona bearing post 202 which is preferably composed from carbon steel. Thebearing assembly 200 includes a linear ball bearing 204 which is locatedbetween the bearing post 202 and a bearing buffer 206. The bearingbuffer 206 allows the linear ball bearing 204 to shift slightly withinthe plunger 198 (to allow for manufacturing tolerances and thermalexpansion). In one embodiment, the bearing buffer 206 is composed ofsilicone.

Energization of the electric solenoid 192 creates a magnetic field whichresults in a force being applied to the plunger 198. The application ofthe force on the plunger and resultant movement of the plunger 198results in the displacement of the thermally conductive liquid 126.

In one embodiment, three bearing assemblies 200 are spaced about theperiphery of the plunger 198. The bearing assemblies keep the plungercentered within the solenoid case. As shown on the right side of FIG.6F, one or more compression springs 208, preferably composed fromstainless steel, located in a respective aperture 210 of the plunger 198support the weight of the plunger 198. In one embodiment, threecompression springs 208 are spaced about the periphery of the plunger198.

As shown in FIG. 6I, in the illustrated embodiment, the plunger 198includes a plunger core 198A and a plunger liner 198B. The plunger 198must be magnetic so that the plunger 198 reacts to the magnetic fieldcreated by the electric solenoid 192. To reduce weight and/or cost, theplunger core 198A may be made from a non-magnetic material, such asaluminum. The plunger liner 198B may be bonded to an outer surface ofthe plunger core 198A (as shown) and composed from a magnetic material,such as 430 stainless steel.

In an alternate embodiment, the actuator 128 includes a pneumaticactuator (instead of an electric solenoid). In one embodiment, thepneumatic actuator includes a plunger and one or more bellows, e.g.,three bellows (see below).

With reference to the exploded view of FIG. 6I, in the illustratedembodiment, the trench 156 includes an inner sub-trench 156A and anouter sub-trench 156B. The inner and outer sub-trenches 156A, 156B areconcentric. The plunger 198 and the solenoid coil 194 and solenoid case196 are concentric and fit within the inner and outer sub-trenches 156A,156B, respectively.

As shown in FIGS. 6F and 6I, the thermal switch 100 includes a membrane140 that is positioned adjacent the plunger 198 of the actuator 128. Inthe illustrated embodiment, the membrane 140 is toroidal or ring-shapedand fits within the circular trench 156. In the illustrated embodiment,an inner edge of the membrane 140 is bonded to the second plate 110. Anouter edge of the membrane 140 is clamped to the solenoid case 196 bythe seal 222.

A middle portion of the membrane 140 is bonded to the plunger 198. Avent ring 218 with laser scored slits allows gas, but not the thermalconduct liquid, to vent between the first reservoir 124 andsolenoid/plunger area. In one embodiment, the vent ring 218 is composedfrom a plastic material, such as polyoxymethylene. A seal 222 creates anouter perimeter of the first reservoir 124. In one embodiment of thepresent invention, the seal 222 has a rectangular cross-section and iscomposed from synthetic rubber, such as a fluoropolymer elastomer.

An up-stop bumper 224 may be bonded to an upper surface of the plunger198 and a down-stop bumper 226 may be bonded to a lower surface of theplunger 198 as shown to minimize impact between the plunger 198 and thefirst and second plates 108, 110, respectively. In one embodiment, thebumpers 224, 226 are composed from a synthetic rubber such as afluoropolymer elastomer material.

Energization of the solenoid coil 194 creates a magnetic field whichacts on the plunger 198. The membrane 140 is connected to the plunger198 and moves with movement thereof.

As discussed above, the channel 114 is formed between an internalsurface of the first side 148 of the switch 100 and a surface of the(center) post 154.

FIGS. 6M and 6N provide views of the internal cavity 112 of the thermalswitch 100 when in the off and on-states, respectively. In theillustrated embodiment, the first reservoir 124 and the dividing plate142 define the plurality of conduction zones 122. As shown, the dividingplate 142 is located above the first reservoir 124. The gas channels 175formed by the dividing plate 142 connect the second reservoir 136 to theconduction zones 122.

As shown in FIG. 6M, when the thermal switch 100 is in the off-state,the actuator 128 is in the second state and the membrane 140 is in thesecond position (see above). When the thermal switch 100 is in the fullyoff-state, the conduction zones 122 are free from the thermallyconductive liquid. Gas from the second reservoir 136 flows through thegas channels 175 and into the conduction zones 122 via the gasentry/exit points 144. In the illustrated embodiment, the gas entry/exitpoints 144 are laser cut into the dividing plate 142. In one embodiment,the depth of the gas entry/exit points 144 may be less than 0.001″ (witha similar width) to ensure that the thermally conductive liquid 126 doesnot enter the gas channels 175. As the thermally conductive liquid 126flows into the gap 120, gas flows via the gas entry/exit points 144 inthe dividing plate 142 into the second reservoir 136. In one embodiment,the second reservoir 136 has a volume much larger than the thermallyconductive liquid displacement volume, so the increase in gas pressuredue to the movement of the thermally conductive liquid 126 is relativelysmall.

The membrane 140 is moveable between the first and second positions inresponse to the actuator 128 being switched from the first state to thesecond state. The thermally conductive liquid 126 is pushed into the gap120 from the first reservoir 124 and gas 138 is pushed from the gap 120to the second reservoir 136 as the membrane 140 is moved from the secondposition to the first position. The thermally conductive liquid 126flows from the conduction zones 122 to the first reservoir 124 and gas138 in the second reservoir 136 flows into the conduction zones 122 inresponse to the membrane 140 being moved from the first position to thesecond position.

The second reservoir 136 is coupled to the second end 118 of the channel114 and contains a gas 138. In the illustrated embodiment, the secondreservoir 136 is located within the post 154. The actuator 128 iscoupled to the first reservoir 124 and the first end 116 of the channel114.

The actuator 128 is coupled to the first reservoir 124 and the channel114. The actuator 128 is moveable between a first state (shown in FIG.6M) and a second state (shown in FIG. 6N) corresponding to the on-stateand the off-state of the thermal switch, respectively. The actuator 128is configured to allow the thermally conductive liquid 126 to flow fromthe first reservoir 124 to the channel 114 when the actuator 128 is inthe first state and to allow the thermally conductive liquid 126 to flowfrom the channel 114 to the first reservoir 124 when the actuator 128 isin the second state.

When the electric solenoid 192 is energized, the plunger 198 and themembrane 140 are moved towards the first position (shown in FIG. 6N).Movement of the membrane 140 towards the first position forces thethermally conductive liquid 126 into the conduction zones 122. The gasthat was in the conduction zones 122 is forced back through the gasentry/exit points 144, through the gas channels 175 and into the secondreservoir 136. The sizing of the gas entry/exit points 144 assists inminimizing or eliminating the risk of thermally conductive liquid 126from entering the gas channels 175. In one embodiment, the height of thegas entry/exit points 144 is less than or equal to 0.002″. In anotherembodiment, the height of the gas entry/exit points 144 is less than orequal to 0.0003″.

Each conduction zone 122 has a width, w_(cz). In one embodiment, thewidth of each conduction zone 122 is less than or equal to 1 inch.

In one embodiment, the height, h_(cz), of each conduction zone 122 isless than or equal to 0.2 inches. In another embodiment, the height,h_(cz), of each conduction zone 122 is less than or equal to 0.1 inches.In still another embodiment, the height, h_(cz), of each conduction zone122 is less than or equal to 0.02 inches.

The gas gap 166 includes a gas entry/exit point 144 between the secondreservoir 136 and the channel 114 (see above). The gas entry/exit point144 configured to minimize entry of the thermally conductive liquid 126into the at least one gas entry/exit point, and thus, the secondreservoir 136. For example, in one embodiment, a height of theentry/exit point 144 (h_(gas_gap)) is less than a height of the gap(h_(cz)). As explained above, the presence of the second reservoir 136allows the liquid metal to flow further into the channel 114 withoutcausing a significant increase in gas pressure within the channel 114.

In the on-state, heat is conducted through the first plate 108, then thegap 120 and conduction zones 122 (which are filled with the thermallyconductive liquid 126) and finally the second plate 110. The first plate108, the thermally conductive liquid 126 in the gap 120 and the secondplate 110 contribute to the overall thermal conductivity of the thermalswitch 100.

Gas Seal

As stated above, the thermally conductive liquid 126 may oxidize in thepresence of oxygen. For example, if a gallium alloy is used, oxidationof gallium will result in a surface layer of gallium oxide which mayinterfere with the operation of the thermal switch 100. Thus,elimination or reduction of the oxygen within the internal cavity 112 ofa device is desirable. The device may be a thermal device, such as athermal switch 100, which during operation has one component that has anoperating temperature higher than another component. In one or more ofthe embodiments of the thermal switch 100 discussed herein, a seal 190may be used to eliminate or reduce the amount of a gas, e.g., oxygen,that is allowed to enter the internal cavity 112 and/or eliminate anygas that does pass into the internal cavity 112.

It should be noted that while the below embodiments are discussed withrespect to the thermal switch 100, the embodiments of the oxygen seal190 may be utilized in any device in which it is desirable to eliminateor reduce the amount of a gas, such as oxygen, that is within or entersan internal cavity.

When a gas needs to be excluded from a vessel, a typical solution wouldbe to form a hermetic seal by any of the many ways known in the art,such as welding or sealing with glass. However, since the thermal switch100 is being used to control conductive heat transfer, one side of thethermal switch 100 will generally have a higher temperature than theother side. The resulting (repeated) differential thermal expansion ofone of the sides of the thermal device poses a significant challenge tomaintaining the integrity of the thermal switch 100.

Thermal expansion is the tendency of material to increase in volume inresponse to an increase in temperature. The amount of expansion varieswith temperature but is often approximated by a linear coefficient ofthermal expansion (CTE). The CTE of aluminum is 23.4×10-6/° C. As anexample, a thermal switch 100 may be circular, composed of aluminum andhave a diameter of 18″. In this example, if the hot side is heated to120° C., while the cold side cooled to 25° C., the hot side expandsrelative to the cold side by 0.040″. So, at the outer diameter of thethermal switch 100, a seal or joint will experience 0.020″ of radialmovement. The fatigue created by repeated cycles of thermal expansionand contraction will result in failure of prior art hermetic seals.

It should be noted that the seal 190 described below may be useful inany device having an internal cavity in which it is desirable torestrict entry and/or eliminate the presence of a gas from the internalcavity 112. Further, in the described embodiment, the gas to berestricted/eliminated is oxygen. However, the seal 190 described belowmay be adapted to restrict entry and/or eliminate the presence of anygas. In one aspect, the seal 190 includes a sealing component 240 and anabsorbing component 242. In the illustrated embodiment, the device 100includes first and second plates 108, 110 which form a housing 146. Thehousing 146 includes an interface 244 formed between the first andsecond plates 108,110. The sealing component 240 is located within thehousing 146 and is coupled to the interface 244 and configured torestrict entry of a gas from the external environment to the internalcavity 112. The absorbing component 242 is located within the housing146 between the sealing component 240 and the internal cavity 112 and isconfigured to absorb a specific gas or gases that pass the sealingcomponent 240.

In a first embodiment as shown in FIG. 7A, a simplified view of thefirst and second plates 108, 110 of an exemplary device 100 is shown. InFIG. 7A, the first and second plates 108, 110 are shown at approximatelythe same temperature, and thus, are the same size. In FIG. 7B, the firstplate 108 is at a higher temperature than the second plate 110, andthus, is shown at a larger size. In the first embodiment, the sealingcomponent 240 includes a flexible seal 240A. The flexible seal 240Aconnects the first and second plates 108, 110 at an outer circumferencethereof. The flexible seal 240A may be made of a flexible material.

In a second embodiment, shown in FIG. 7C, the sealing component 240 mayinclude an O-ring 240B. The O-ring 240B may be located within a trenchin one or both of the first and second plates 108, 110 (not shown).

In a third embodiment, the sealing component 240 may include a seal 240Cmade from an elastomer which is bonded to the first and second plates108, 110. In the first three embodiments, the sealing elements 240A,240B, or 240C are in direct contact with the first plate 108.Consequently, the temperature of the sealing element is elevated duringoperation of the thermal switch. Elevated temperature may contribute toa high level of gas permeation through the sealing element.

Gas permeation is the penetration of a gas through a solid. It resultsfrom the diffusion of a permeant gas through the solid material. Therate of diffusion as a function of temperature generally follows anArrhenius relationship. Consequently, the rate of permeation increasesin a roughly exponentially manner with increasing temperature, with alesser effect contributed by any temperature dependence of gassolubility. Elastomer materials, whose flexibility would otherwise makethem a desirable seal material, are particularly susceptible to gaspermeation. The elevated elastomer temperature present in the previousseal embodiments makes them unacceptable for some uses of a thermalswitch.

With reference FIGS. 7E and 7E-1, a fourth embodiment of the seal 190 isshown. In the fourth embodiment, the seal 190 is utilized in a thermaldevice, such as a thermal switch 100. The thermal switch 100 has ahousing 146 formed from a first plate 108 and a second plate 110 whichare coupled together using a plurality of fasteners, such as bolts (notshown). The housing 146 has a first side 148 and a second side 150 andmay have a square or circular cross-section (or footprint), see FIGS. 4Aand 6A. A partial cross-section of the thermal device 100 is shown inFIG. 7E.

The first and second plates 108, 110 are separated by a plastic shim 246forming an interface 244 between an internal cavity 112 and the exteriorenvironment. The plastic shim 246 supports the bolt load, spaces thefirst and second plates 108, 110 at a desired separation, and allowssliding movement as the first plate 108 expands thermally.

The seal 190 includes a sealing component 240 and an absorbing component242. The sealing component 240 is located within the housing 146 andcoupled to the interface 244. The interface 244 is located within theseam between the first and second plates 108, 110 and traverses theouter perimeter of the housing 146. The sealing component 240 isconfigured to restrict entry of a gas, e.g., oxygen, from the externalenvironment to the internal cavity. The absorbing component 242 islocated within the housing 146 between the sealing component 240 and theinternal cavity 112 configured to absorb any gas, e.g., oxygen, thatpasses the sealing component 240.

The sealing component 240 includes a first cavity 258 within the housing146. In the illustrated embodiment (see in particular FIG. 7E-1), thefirst cavity 258 is trench that has a toroidal shape that traverses theouter perimeter of the housing 146. The first cavity or trench 258 iscoupled to the interface 244 and surrounds the internal cavity 112. Asshown, in the illustrated embodiment the first trench 258 contains a gasblocking material 260, such as grease or vacuum grease.

In one embodiment, the blocking material 260 has an oxygen permeabilityless than

$5000\frac{\;{{cm}^{3} \cdot {mm}}}{m^{2} \cdot {day} \cdot {atm}}$

at 25° C. and a viscosity less than 1000 Pa·s at 25° C. In anotherembodiment, hydrocarbon vacuum grease is utilized as the gas (oxygen)blocking material 260. Hydrocarbon vacuum grease is composed ofextremely high molecular weight hydrocarbons, and consequently has lowvapor pressure. Low vapor pressure enables injection into the firstcavity 258 with minimal voids, which if present may create a path forrapid oxygen diffusion. Evacuating the first cavity 258 prior toinjecting the gas blocking material 260 minimizes voids, however thecavity 258 may be evacuated to a minimum pressure no lower than thevapor pressure of the blocking material 260.

The viscosity of hydrocarbon vacuum grease decreases significantly withincreasing temperature (more so than silicone based vacuum grease). Thisvariation may be employed when the hydrocarbon grease is injected intocavity 258. Decreased viscosity will allow injection at moderatepressure. The grease may be heated for the purpose of mixing in oxygenabsorbing materials (see below). The hydrocarbon grease may be heatedfor mixing and then cooled quickly to create a stable suspension ofotherwise immiscible components. The thermal expansion of hydrocarbongrease (approximately 0.1%/° C. may be utilized as a passive actuationmechanism (as discussed below). One suitable hydrocarbon vacuum greaseis available from Kurt J Lesker Company under the tradename Apiezon.

The absorbing component 242 includes a second cavity 262 within thehousing 146. In the illustrated embodiment, the second cavity 262 is atrench that has a toroidal shape that traverses the outer perimeter ofthe housing 146. As shown, the second cavity or trench 262 is coupled tothe interface 244 and surrounds the internal cavity 112. The secondtrench 262 of the absorbing component 242 contains a gas absorbingmaterial 264. In one embodiment, the gas absorbing material 264 includesa composition that includes a polyunsaturated fatty acid, e.g., linoleicor oleic acid mixed with a metal catalyst, e.g., iron oleate and anon-organic binder, e.g., magnesium oxide. One suitable gas absorbingmaterial is available from Mitsubishi Gas Chemical America under thetrademark RP System®. In another embodiment, a copper-based catalyst maybe used, such as the copper-based catalyst R3-11 available from BASF. Inyet another embodiment, an oxygen absorbing material including ironpowder may be used.

It should be noted that the first and second trenches 258, 262 may bethe same trench and the gas blocking material 260 and the gas absorbingmaterial 264 may be mixed and/or combined together.

The sealing component 240 may include an isolating element 266 thatextends from the one of the first and second plates 108, 110 into thefirst trench 258. In the illustrated embodiment, as shown in FIG. 7E,the isolating element 266 forms a gap 268 between the isolating elementand the other one of the first and second plates 108, 110. As shown, thegap 268 is filled with the gas blocking material 260.

In one embodiment, the isolating element 266 includes a fin 270extending from the one of the first and second plates 108,110 and aflange 272 connected to the fin 270. As shown, in the illustratedembodiment, the fin 270 extends from the first plate 108 and the gap 268is located between the flange 272 and the second plate 110. A pluralityof O-rings 274A, 274B, 274C separate the first trench 258 from theexternal environment, the first and second trenches 258, 262, and thesecond trench 262 from the internal cavity 112.

The fin 270 provides thermal isolation such that the flange 272 remainscool, with a temperature close to that of the second plate 110. Asexplained above, the rate of permeation increases exponentially withtemperature, so to create an effective gas seal, the temperature of thegas blocking material 260 must be minimized. The gap 268 between theflange 272 and the second plate 110 is the location where the permeationof oxygen is most restricted. It is narrow, long, and has a reducedtemperature, thus creating an optimal oxygen seal, while stillpermitting relative movement of the flange 272 and the second plate 110.In the illustrated embodiment, the fin and flange 270, 272 are machinedfeatures of the first plate 108. Alternatively an isolating element maybe formed by joining a separate component to the first plate 108 bymeans of soldering or brazing, mechanical fastening, press fitting, orby pressing the component against the first plate 108 by means of aspring or other elastic component. The isolating element 266 may be afin made out of the same material as the first plate 108, asillustrated, or alternately, a component formed of a material with lowthermal conductivity.

The third O-ring 274C seals a volume of the second trench 262 filledwith the oxygen absorbing material 264. The third O-ring 274C causes theoxygen permeating past the sealing component 240 to dwell in the secondtrench 262 sufficiently long to react with the absorbing material 264.

The first O-ring 274A, the sealing component 240 and the second O-ring274B create a first oxygen seal that is aimed at eliminating or reducingthe amount of oxygen that enters the internal cavity 112 from theexternal environment. However, a small amount of oxygen may pass thisfirst seal 274A, 240, 274B. In this embodiment, the third O-ring 274Cacts as a second oxygen seal that traps the any oxygen that does passthe first oxygen seal 274A, 240, 274B, trapping the oxygen in theabsorbing component 242 to allow it to be absorbed by the gas absorbingmaterial 264.

Some variations on the basic design shown in FIG. 7E may be desirable,depending on the requirements of a particular thermal application, e.g.,operating temperature, switch size, structural loads, etc. . . . .

With reference to FIG. 7F, rectangular seal elements 276 may be used inplace of the O-rings 274A, 274B, 274C. The advantage of usingrectangular seal elements is that the thermal expansion of the firstplate 108 may result in flexing of the rectangular seal elements 276(rather than the O-rings 274A, 274B, 274C sliding on the first plate108). This may be beneficial in larger switch designs, where therelative movement of the first and second plates 108, 110 is larger andthere is a greater risk of grease leaking past the O-ring(s) as a resultof the repeated sliding movement. For smaller switches, O-rings may havesufficient lateral flexibility so that sliding would not occur, and thusrectangular seals would be unnecessary. It should also be noted, that asshown in FIG. 7F, the isolating element 266 is physically connected to,or extends from, the first plate 108.

With reference to FIG. 7G, in another embodiment, an adhesive material278 is used to bond the rectangular elastomer seal elements 276 to thefirst and second plates 108, 110. The rectangular seal elements 276 arecapable of supporting a structural load, thus the need for bolts orfasteners to couple the first and second plates 108, 110 may beeliminated. Contact between the first and second plates 108, 110 via theshim 246, could also be eliminated. It should be noted that theembodiment shown in FIG. 7G may result in a lower maximum operatingtemperature of the thermal switch 100. Adhesives capable of bonding anelastomer to a metal may have a lower maximum operating temperature thanthe elastomer itself. Additionally, the bonded seal would support lessstructural load than a bolted design.

In applications where space within the thermal device is limited, it maybe desirable to eliminate the second trench 262, i.e., a separate oxygenabsorber reservoir, by incorporating the gas (oxygen) absorbing materialinto the gas (oxygen) blocking material 260. For example, it may bepossible to mix a liquid fatty acid, along with a metal catalyst,directly into the grease.

Further, in other embodiments, other materials may be added to thevacuum grease for the purpose of decreasing oxygen permeability, whichmay allow the cooler side of the thermal switch to be operated at evenhigher temperatures than otherwise achievable.

Nanoclays are naturally occurring minerals which can be exfoliated intoextremely thin plate-like particles and can be used as an additive topolymer materials to decrease gas permeability. Adding a nanoclay tovacuum grease may further decrease gas permeability.

In alternative embodiments, gas or oxygen seals that do not use vacuumgrease might be feasible for some applications, particularly those wherethe diameter of the thermal device is small and the temperaturedifferential between the hot and cold side is relatively small.

For example, in an aluminum thermal switch 100 with outer diameter 3″with a maximum temperature differential of 60° C., the flange of theoxygen seal would translate by 0.002″ relative to the bottom plate. In aseal gap 0.004″ high, this creates 50% shear strain in the materialbetween the flange and bottom plate. A sufficiently flexible adhesive279, as shown in FIG. 7H, may be used as the gas blocking material 260(in place of the vacuum grease).

The gas seal created by the adhesive 279 may allow the first and secondO-rings 274A, 274B to be eliminated.

With reference to FIG. 7I, for applications operating at relatively lowtemperatures, thermal isolation of the sealing material may not benecessary. If the thermal device 100 is also of relatively smalldiameter, then a reasonably thin layer of adhesive 280 could accommodatethermal expansion. Oxygen permeation through the thin adhesive bond maybe low enough to be absorbed by a moderate quantity of oxygen absorbingmaterial 264.

INDUSTRIAL APPLICABILITY

With reference to the drawings and in operation, the present inventionprovides a thermal device 400 that includes a thermal switch 402 (see inparticular FIGS. 8-12). In general, the thermal device 400 may be usedto control a temperature or temperature profile of a controlledcomponent 404. The controlled component 404 may be any type of componentfor which thermal control is desirable. For example, the controlledcomponent 404 could be a part of a product during a manufacturingprocess, a part of a machine used to manufacture another product, asensor or instrument, or any other component of a thermal system.Non-limiting examples of thermal systems in which the thermal device 400could be used include vessels for chemical reaction, automotive thermalsystems, such as for batteries or fuel cells, HVAC systems,thermoelectric cooling, thermoelectric power generation, power controlsystems, solid-state lasers and laser diodes, thermal testing equipment,aerospace systems including spacecraft and satellites, thermal energystorage, or a temperature dependent manufacturing process, e.g., asemiconductor manufacturing process. In some embodiments, the controlledcomponent 404 may be the first plate 108 of the thermal switch 402.

The thermal device 400 includes a thermal switch 402. A suitable thermalswitch 402 could be any one of the embodiments of the thermal switch100, 402, 506, 700, 800, 1100, 1200 disclosed herein or any othersuitable switch. With particular reference to FIG. 8, the thermal device400 controls a temperature associated with the controlled component 404.The thermal switch 402 has an on-state and an off-state and includes afirst plate 108 and a second plate 110. The first and second plates 108,110 are composed from a thermally conductive material such as aluminum.The first plate 108 is thermally coupled to the controlled component404. The thermal device 400 includes a heat sink 406 coupled to thesecond plate 110. The first and second plates 108, 110 are connected toform an internal cavity 112 that has a channel 114 defining a gap 120between the first and second plates 108. 110. The thermal switch 400includes a first reservoir 124 and an actuator 128. The first reservoir124 is coupled to the channel 114 and contains a thermally conductiveliquid 126. The actuator 128 is coupled to the first reservoir 124 andthe channel 114 and is moveable between a first state and a second statecorresponding to the on-state and the off-state of the thermal switch402, respectively. The actuator 128 is configured to allow the thermallyconductive liquid 126 to flow from the first reservoir 124 to thechannel 114 when the actuator 128 is in the first state and to allow thethermally conductive liquid 126 to flow from the channel 114 to thefirst reservoir 124 when the actuator 128 is in the second state.

The general thermal device 400 shown in FIG. 8 may be used in a varietyof applications. In some applications, the controlled component 404 maybe thought of as a heat source and the heat sink 406 may be thought as asecond controlled component. The thermal switch 402 may be thermallycoupled between these components 404, 406 to control a temperaturedifferential therebetween. For example, one of the two components may bea heat source or sink that cannot be readily turned on and off, such asa heat pipe. Use of the thermal device 400 may be used to control thetemperature of such a heat source or heat sink.

With specific reference to FIG. 9, alternatively, the controlledcomponent 404 may be a thermoelectric cooler. A thermoelectric cooler(also known as a Peltier cooler) is a solid-state heat pump. The Peltiereffect—the conversion of an electric voltage to a temperaturedifferential—is utilized to generate heat flux. The thermal device 400may be used to control a temperature or temperature profile of thethermoelectric cooler 404. In the illustrated embodiment, thethermoelectric cooler 404 is connected to an external surface of thefirst plate 108. A component 407 (such as a sensor or laser diode) iscoupled to the top surface of the thermoelectric cooler 404. Thetemperature of the component 407 may be controlled by modulation of thethermoelectric cooler 404. The thermal switch 402 controls heat transferbetween the thermoelectric cooler 404 and the heat sink 406. When thethermoelectric cooler 404 is unpowered, a thermally conductive pathbetween the component 407 and heat sink 406 would normally be created,resulting in heat flowing backwards from the heat sink 406 to thecomponent 407. The thermal switch 402 may be used to decouple thecomponent 407 and heat sink 406, leading to improved system efficiency.As shown, in the illustrated embodiment, the heat sink 406 is anexternal air-cooled heat sink that is connected to an external surfaceof the second plate 110 via, for example, bolts. Alternatively, theexternal air-cooled heating sink may be unitarily formed, i.e., integralwith, the second plate 110. Other types of heat sinks may also be used,for example, a liquid cooled heat sink (see below). Also, as notedabove, the thermal switch 402 is similar to the fourth embodiment of thethermal switch 100 discussed above, however, any suitable thermal switchmay be used.

With reference to FIG. 10, the thermal device 400 may be configured toact as a variable cooling plate. In this embodiment, the controlledcomponent 404 may be a heat generating component which is thermallycoupled to the first plate 108. The heat sink 406 may be implemented bya plurality of cooling channels within the second plate 110. A variablecooling plate would provide a simple and efficient means of activelycontrolling the temperature of the heat generating component, ascompared to prior art solutions such as varying the temperature or flowrate of a coolant.

With reference to FIG. 11, a heating device 408, for example, a filmheater, strip heater, cast heater or the like is integral to the firstplate 108, which may be coupled to the controlled component or workpiece404. Control of the temperature of the heating device 408, and thus theheat transferred to the controlled component or workpiece 404, may beaccomplished solely by the thermal switch 402 or by thermal switch 402in conjunction with modulation of the heating device 408. In eithercase, efficiency and performance better than control by constant coolingand heater modulation may be achieved (see further examples below).

With reference to FIG. 12, the thermal device 400 may act as a variableliquid to liquid heat exchanger. In the illustrated embodiment, thecontrolled component 404 is a first liquid-based thermal coupling device410. The first liquid-based thermal coupling device 410 includes one ormore channels within the first plate 108 through which a liquid ispassed. The heat sink 406 is implemented by a second liquid-basedthermal coupling device 412. In the illustrated embodiment, the secondliquid-based thermal coupling device 412 includes one or more channelswithin the second plate 110 through which a liquid is passed. The firstliquid-based coupling device 410 and the second liquid-based thermalcoupling device 412 and the switch 402 form a variable liquid-liquidheat exchanger. A variable liquid to liquid heat exchanger may be usedas a simple and compact means of controlling heat transfer between twocirculating liquids, avoiding the complexity of flow control valves orvariable pumping rates. Similar embodiments may control the heattransfer between gases or air, in thermal systems where the heat sink orsource operates by radiative heat transfer, or any combination thereof.

Thermal Switch for Semiconductor Manufacturing Basic Devices

Thermal control, and its optimization, is uniquely important andvaluable in the semiconductor manufacturing industry. During themanufacturing of semiconductor devices such as processors and memory, asilicon wafer goes through dozens of processing steps. These steps (suchas deposition and etch steps) typically occur in a process module. Thetemperature of the wafer and the components of the process module mustbe precisely controlled during the processing of the wafer to achieveoptimal process results. In the context of semiconductor manufacturing“thermal precision” may be considered to include any aspects oftemperature control that may affect wafer performance, yield, orthroughput. As such, transient temperature control, including control ofrapid transients, must be considered, wherein thermal precision wouldrequire conforming to a desired transient.

The complex operating conditions of a process module may complicate thecontrol of wafer and component temperature. For example, etch anddeposition steps often make use of plasma, which may create largechanges in thermal loads as the plasma is switched on and off.Additionally, in some process modules it is desirable to quickly changethe temperature of the wafer or a chamber component. The thermal switchof the present invention which utilizes a thermally conductive liquid,such as a liquid metal, is particularly beneficial in semiconductormanufacturing, testing or other related processes.

With reference to FIG. 13A, a diagrammatic representation of anillustrative process module 500 is shown. During a testing,manufacturing or other process, the process module 500 performs amanufacturing step while simultaneously controlling a temperature ortemperature profile of a semiconductor wafer 502. The term semiconductorwafer includes, but is not limited to, a silicon wafer, siliconsubstrate, semiconductor based integrated circuit and the like. Theprocess module 500 includes a processing chamber 504 which is configuredto receive the wafer 502. One suitable process module and processingchamber is disclosed in U.S. Pat. No. 8,313,610, issued on Nov. 2, 2012,to Lam Research Corporation, (the '610 patent) which is herebyincorporated by reference. It should be noted, however, that the presentinvention may be used with any suitable process module and/or processwhich may benefit from improved thermal control of a wafer or processmodule component, including but not limited to photoresist development,photoresist strip, ion implantation, wafer anneal, chemical vapordeposition, physical vapor deposition, and atomic layer deposition.

Returning to FIG. 13A, the process module 500 includes at least onethermal switch 506 coupled to the processing chamber 504. The thermalswitch 506 may be any suitable thermal switch. In the illustratedembodiment, the thermal switch 506 is a thermally conductive liquidbased thermal switch and may be of any one of the embodiments disclosedherein. The thermal switch 506 includes a first plate 108 and a secondplate 110 which are composed from a thermally conductive material, suchas aluminum. The first and second plates 108, 110 are connected to forman internal cavity 112 (see above). The internal cavity 112 has achannel 114 that defines a gap 120 between the first and second plates108, 110. The thermal switch 506 also includes a reservoir 124 coupledto the channel 114. The reservoir 124 contains a thermally conductiveliquid 126. The actuator 128 is coupled to the reservoir 124 and thechannel 114 and is moveable between a first state and a second statecorresponding to an on-state and an off-state of the thermal switch 506respectively. The actuator 128 is configured to allow the thermallyconductive liquid 126 to flow from the reservoir 124 to the channel 114when the actuator 128 is in the first state and to allow the thermallyconductive liquid 126 to flow from the channel 114 to the reservoir 124when the actuator 128 is in the second state. In the illustratedembodiment, during the manufacturing or testing process, heat is appliedto the wafer 502 from a heat source (not shown in FIG. 13A). The heatsource may be one or more of a plasma, a radiant heater, a hot gas orliquid, a laser, an exothermic chemical reaction, and other suitablesource.

The thermal switch 506 may act as an adjustable cooling plate, allowinga temperature associated with the wafer 502 to be controlled. As shownin FIG. 13A, a heat sink 508 acts to direct heat away from the internalcavity 112 (and the first plate 108). In the embodiment shown in FIG.13A, the heat sink 508 may include one or more cooling channels 510through which a coolant flows.

With reference to FIG. 13B, the thermal switch 506 may include a heatsource 512 which is integral with, or coupled to, the first plate 108for heating the wafer 502. In the illustrated embodiment, the heatsource 512 is a cast aluminum heater integral with the first plate 108.

With reference to FIG. 13C, the heat source 512 is integral with thefirst plate 108. The thermal switch may be used to alternately heat orcool a controlled component or assembly. As shown, an assembly 514 couldbe coupled to the first plate 108. For example, in a capacitivelycoupled plasma etching process module, the assembly 514 and the thermalswitch 506 may form a top electrode (see below).

With reference to FIG. 13D, the process module 500 may be configured tocontrol the temperature of a device 518 that is under test. The device518 may be a heat generating device. It may be desirable to rapidly heatand/or cool the device 518. Rapid heating and cooling may be achievedusing the assembly 514 by decreasing the thermal conductivity of thethermal switch 506 while the device 518 is being heated and increasingthe thermal conductivity while cooling the device 518.

With reference to FIG. 13E, the heat sink 508 may be an external heatsink 508 that is thermally coupled to the second plate 110. In theillustrated embodiment the external heat sink 508 includes coolingchannels 510 through which a liquid coolant could be passed. Otherpossible heat sinks include a heat pipe or the evaporator of arefrigeration system.

The process module 500 may include a retention device 520, such as anelectrostatic chuck (ESC) for supporting and/or holding the wafer 502 inplace. In FIG. 13F, a ceramic plate 522 may be bonded to the first plate108 and serve as a heat source via embedded heating elements and chuckthe wafer via an embedded chucking electrode (not shown, see below).While the illustrated embodiment makes reference to an ESC, theretention device 520 may include any means of holding and/or supportingthe wafer including, but not limited to vacuum chucks (utilizing gaspressure to secure the wafer) or wafer supports (with the wafer heldonly by gravity).

With reference to FIG. 13G, in another embodiment, a separate heater 518and ceramic plate 522 may be provided.

With reference to FIG. 13H, in the processing chamber 504 of aninductively coupled plasma etch process module 500, energy from a RFgenerator is directed into a plasma cavity 530 via a wire coil 526 abovethe processing chamber 504. The processing chamber 504 includes a vessel504A that is capped with a ceramic component 504B forming an internalplasma cavity 530. The vessel 504A may be made of any suitable material,including, but not limited to aluminum or stainless steel. In theillustrated embodiment the ceramic component is a plate. In otherembodiments the ceramic component may be a dome or a cylinder. The wirecoil 526 is positioned above the ceramic component 504B. The ceramiccomponent 504B is electrically non-conductive and allows theelectro-magnetic field generated by the wire coil 526 to penetrate theprocessing chamber 504. Gases enter the plasma cavity 530 where they areconverted to reactive species which etch the wafer 502. Volatile etchbyproducts are exhausted to a vacuum pump (not shown). As shown, athermal switch 506 may be coupled to the retention device 520 to controla temperature of the wafer 502. The thermal switch may be of any of theembodiment disclosed herein or any suitable thermally conductive liquidbased thermal switch.

With reference to FIG. 13I, a thermal switch 506 may also be locatedwithin a junction 504C between the vessel 504A and ceramic component504B of the processing chamber 504 of an inductively coupled plasma etchprocess module 500. The thermal switch 506 allows improved, directcontrol of the thermal interface between the vessel 504A and the ceramicplate 504B.

With reference to FIG. 13J, in the processing chamber 504 of acapacitively coupled plasma the process module 500, alternating electriccurrent, which may be in the radio frequency (RF) range, is applied totwo electrodes (see below), creating plasma in the cavity 530. Theprocessing chamber 504 may be generally composed from aluminum, formingan internal plasma cavity 530. The processing chamber 504 includes a topelectrode 532 and the retention device 520 (which serves as a bottomelectrode). In the illustrated embodiment, the retention device 520 isillustrated as an ESC, however, the present invention is not limited toa processing chamber 504 that includes an ESC. Gases flow through thetop electrode 532 and are ionized in the plasma cavity 530. The wafer502 is etched by ion bombardment and etch byproducts are exhausted to avacuum pump (not shown). The top electrode 532 includes top electrodetemperature control assembly 534 and the ESC 520 includes a retentiondevice temperature control assembly 536. The top electrode temperaturecontrol assembly 534 and the retention device temperature controlassembly 536 each include one or more thermal switches 506. The thermalswitch(es) may be of any of the embodiment disclosed herein or anysuitable thermally conductive liquid based thermal switch.

Thermal Device with Multiple Switches for Spatial Control

As described above, thermal precision is critical in semiconductormanufacturing. For some components, and particularly with reference to awafer, thermal precision further includes spatial control oftemperature, that is controlling temperature at all points on a surface,sometimes referred to as a temperature profile. For example, it may bedesirable to achieve either spatial uniformity or to conform to aprescribed, non-uniform temperature profile on a working surface orwafer. In components such as ceramic components, controlling thetemperature profile of the component may be important to minimize stressor wear. Controlling the temperature profile of a wafer is critical toachieving optimal process results. The temperature profile of a wafermay have a radial component (for example vary from center to edge) aswell as non-radial components (for example a side-to-side variation).Various temperature profiles may be desirable depending on the specificsof a particular process module and process.

Thermal devices with multiple switches may be utilized to control thetemperature profile on a working surface or workpiece. With reference toFIG. 14A, the working surface may be a surface of one of the first orsecond plates 108, 110, a surface of a controlled component, or asurface thermally coupled to a controlled component. The controlledcomponent may be a workpiece, e.g., in a manufacturing or testingprocess, or a component in a manufacturing or testing apparatus. In oneaspect of the present invention, the temperature profile of a workingsurface may be controlled using independent control of two or morethermal switches.

With reference to FIG. 14A, a thermal device 600 for controlling forcontrolling a temperature profile of a working surface 602 includes afirst and second plates 108, 110. The first and second plates 108, 110are composed from a thermally conductive material and are connected toform first and second internal cavities 112A, 112B. An outer surface ofone of the first and second plates 108, 110 forms the working surface602. The thermal device 600 includes a thermal switch 100A, 100B locatedwithin respective internal cavities 112A, 112B. Each thermal switch100A, 110B has an on-state and an off-state and includes a channel 114A,114B, a first reservoir 124A, 124B and an actuator 128A, 128B. Eachchannel 114A, 114B defines a gap 120 in the respective internal cavity112A, 112B between the first and second plates 108, 110. The firstreservoirs 124A, 124B are coupled to the respective channel 114A, 114Band contain a thermally conductive liquid 126.

Each actuator 128A, 128B is coupled to the respective first reservoir124A, 124B and respective channel 114A, 114B. The actuators 128A, 128Bare moveable between a first state and a second state corresponding tothe on-state and the off-state of the respective thermal switch 100A,100B, respectively, and are configured to allow the thermally conductiveliquid 126 to flow from the respective reservoir 124A, 124B to therespective channel 114A, 114B when the actuator 128A, 128B is in thefirst state and to allow the thermally conductive liquid 126 to flowfrom the respective channel 114A, 114B to the respective first reservoir124A, 124B when the actuator 128A, 128B is in the second state.

Each thermal switch 100A, 100B is formed by a portion of the first andsecond plates 108, 110 and the respective channel 114A, 114B, firstreservoir 124A, 124B, actuator 128A, 128B. The thermal switches 100A,100B, may be of the form or any one of the embodiments disclosed herein.

With reference to FIGS. 14B and 14C, one or more of the switches 100 inthe thermal device 600 may be ring shaped switches (see above). As shownin the illustrated embodiment, the first switch 100A is centrallylocated with the thermal device 600. The second switch 100B is aring-shaped switch 100B located within a ring-shaped internal cavity (ortrench) 112B. For purposes of illustration, the first switch 100A isshown in the on state, while the second switch 100B is shown in theoff-state.

Thermal Switch with Pneumatic Actuator

In some applications, minimizing the separation between adjacent thermalswitch gaps may be an important consideration. Wide separation betweenswitch gaps may prevent achieving some desired temperature profiles. Inprevious embodiments, adjacent switch gaps are separated by at minimum,the width of the plunger and solenoid case. With reference to FIGS. 15Aand 15B in another embodiment of the present invention, a thermal switch700 includes a pneumatic actuator 728. FIGS. 15A and 15B show partialcutaway views of the thermal switch 700 in the open and closedpositions, respectively. The illustrated actuator arrangement eliminatesthe solenoid case and thus the distance between adjacent switch gaps 720may be smaller.

As shown, the thermal switch 700 includes a first plate 708 and a secondplate 710 and a pneumatic actuator 728. The first and second plates 708,710 are composed from a thermally conductive material. The first andsecond plates 708, 710 are connected to form an internal cavity 712. Theinternal cavity 712 has a channel 714 that defines a gap 720 a gapbetween the first and second plate 708, 710. The thermal switch 700further includes a reservoir 724 coupled to the channel 714 thatcontains a thermally conductive liquid 726. As shown, the pneumaticactuator 728 is coupled to the first reservoir 724 and the channel 714and is moveable between a first state (shown in FIG. 15B) and a secondstate (shown in FIG. 15A) corresponding to the on-state and theoff-state of the thermal switch 700, respectively. The pneumaticactuator 728 is configured to allow the thermally conductive liquid 726to flow from the reservoir 724 to the channel 714 when the pneumaticactuator 728 is in the first state and to allow the thermally conductiveliquid 726 to flow from the channel 714 to the first reservoir 724 whenthe actuator 728 is in the second state.

The internal cavity 712 of the thermal switch 700 may be located in acentral area of a housing formed by the first and second plates 708,710. Alternatively, the internal cavity 712 may be a trench whichsurrounds a central post (see above). Other features and/or alternativesmay be as is found in any of the other embodiments disclosed herein.

In the illustrated embodiment the pneumatic actuator 728 includes asource of pressurized air 728A, a bellows 728B, and a plunger 728C. Thesource of pressurized air 728A is controllably coupled to the bellows728B. The plunger 728C is coupled to the bellows 728B and is moveablebetween first and second positions corresponding to the first and secondstates of the pneumatic actuators respectively.

In one embodiment, the bellows 728B acts on the plunger 728C to move theplunger 728C from the second position to the first position whenpressurized air from the source of pressurized air 728A is applied tothe bellows 728B. Further, a return spring 728D may be coupled to thebellows 728B and configured to move the plunger 728C from the firstposition to the second position when the source of pressurized air 728Ais removed from the bellows.

Exemplary Thermal Switch for Use in a Capacitively Coupled PlasmaProcess Module

As discussed above, in a capacitively coupled plasma process module 500,radio frequency alternating current is applied directly to a topelectrode 532 and an electrostatic chuck (ESC) 520, which serves as abottom electrode. One such process module 500 is disclosed in the '610patent referenced above. With reference to FIGS. 16A-16F and FIGS.17A-17H, as discussed in more detail below, thermal switches accordingto various embodiments of the present invention may be incorporated intothe top electrode 532 and the bottom electrode 520.

Generally, the top electrode 532 is bolted to an upper portion of analuminum vacuum chamber. The ESC 520 is bolted to an assembly known asthe “bias housing” which has an internal cavity and includes electricaland gas connections to the ESC 520, as well as actuators for the pinsused to lift the wafer. The wafer passes into and out of the chamber viaa slot which is connected via a valve to a transfer chamber.

In the prior art top electrode, a temperature control assembly, whichmay comprise a cooling plate, a heater plate, and thermal choke ringsdisposed therebetween, serves either to heat or cool the top electrodedepending on operating conditions. Coolant circulates through channelsin the cooling plate, providing constant cooling. The thermal chokerings create a controlled, but fixed, amount of thermal resistancebetween the heater plate and cooling plate, such that a largetemperature differential may be maintained when desired. Temperaturecontrol is achieved by modulating the power delivered to the heaterelements in the heater plate. This prior art arrangement has notableshortcomings including inefficiency and limited thermal performance.

Top Electrode with Thermal Switches

In the illustrated embodiment shown in FIGS. 16A-16J, in one embodimentof the present invention, the top electrode 532 includes a top electrodetemperature control assembly 534 having a plurality of thermal switches800. The prior art thermal choke rings (which create a non-varyingthermal resistance between a cooling plate and heater plate) arereplaced by thermal switches 800 so that thermal resistance between thecooling plate and the heating plate may be varied, enabling improvedefficiency and thermal performance. The resistance of the thermalswitches may, for example, be decreased to enable faster cooling of thetop electrode, or increased to allow faster heating or more efficientoperation (i.e. a temperature differential between the cooling plate andheater plate may be maintained with a decreased amount of powerdelivered to the heater plate).

As shown in the cut-away cross section view of FIG. 16A, an exemplarytemperature control assembly 534 includes a plurality of thermalswitches 800. The temperature control assembly 534 includes a first (orheating) plate 808 and a second (or cooling) plate 810. In theillustrated embodiment, the top electrode temperature control assembly534 has generally circular top and bottom surfaces 534A, 534B. Eachthermal switch 800 is toroidal or ring shaped (similar to the thermalswitch in the fourth embodiment discussed above). In the illustratedembodiment, the temperature control assembly 534 includes first, secondand third ring shaped concentric thermal switches 800A, 800B, 800C. Eachthermal switch 800A, 800B, 800C is located adjacent, and controls thethermal resistance, in a respective ring-shaped portion or zone 801A,801B, 801C of an interface 801 between the first and second plates 808,810.

The first plate 808 and the second plate 810 are bolted together withplastic shims 802 therebetween. The second or cooling plate 810 includescooling channels 804 for circulating coolant. The first or the heaterplate 808 has embedded heater elements 806. In the illustratedembodiment, the top electrode includes three thermal switches 800A,800B, 800C, however, it should be noted that any number of thermalswitches 800 may be used. Each thermal switch 800 provides variablethermal resistance in a respective portion of the interface between thefirst and second plates 808, 810.

The first and second plates 808, 810 are composed from a thermallyconductive material, such as aluminum. Each switch 800 has an internalcavity 812, a first reservoir 824, and an actuator 828. The internalcavity 812 includes a channel 814 that defines a gap 820 between thefirst and second plates 808, 810. The first reservoir 824 is coupled tothe channel 814. The first reservoir 824 contains a thermally conductiveliquid 826. The actuator 828 is coupled to the first reservoir 824 andthe channel 814 and is moveable between a first state and a second statecorresponding to the on-state and the off-state of the respectivethermal switch 800. The actuator 828 is configured to allow thethermally conductive liquid 826 to flow from the first reservoir 824 tothe channel 814 when the actuator 828 is in the first state and to allowthe thermally conductive liquid 826 to flow from the channel 814 to thefirst reservoir 824 when the actuator 828 is in the second state.

In the illustrated embodiment, the actuator 828 is an electric solenoid.However, it should be noted that other types of actuators, for example,a pneumatic actuator, may also be used. Each thermal switch 800 includesa solenoid 892 with a solenoid or wire coil 894 and solenoid case 896. Aplunger 898 is held in place by a linear ball bearing 904 sliding on abearing post 902. The weight of the plunger 898 is supported by acompression spring 908 which push the plunger 898 to the switch openposition. The solenoid 892 pulls the plunger 898 to the switch closedposition (which forces the thermally conductive liquid 826 into the gap820). A second (or gas) reservoir 836 accommodates the gas displacedwhen thermally conductive liquid 826 moves into the gap 820. In theillustrated embodiment, the second reservoir 836 is in the form of acircular channel.

Each thermal switch 800 further includes a diaphragm or membrane 840retained by clamp rings 912, 914 and connected to the plunger 898 with arib 916. A vent ring 918 with laser scored slits allow gas, but not thethermally conductive liquid, to vent between the first reservoir 824 andthe solenoid/plunger area.

A dividing plate 842 with laser scored vents provides the gas pathbetween the gap 820 and the second reservoir 836. In one embodiment, thedividing plate 842 (and other plastic components of the thermal switches800) are composed from a polyimide material, such as Kapton filmavailable from Dupont or Cirlex Kapton laminates available from Fralock.Polyimide film has a CTE (20×10-6/° C.) similar to the CTE of aluminum(24×10-6/° C.). Since the dividing plate 842 (and the other plasticparts) are large (up to 17″ diameter, it is critical that thermalexpansion be minimized.

It should be noted that in the illustrated embodiment, the gap 820 ofeach thermal switch 800 does not have sub-channels. The required thermalresistance may be achieved with a gap of length less than or equal to0.2″, so a simple implementation as illustration is best suited to thisembodiment.

As shown, the temperature control assembly 534 may include a pluralityof feedthrough apertures 807 to allow for the passage of bolts (notshown). The bolts are used to secure other components comprising the topelectrode, e.g., a backing plate. Other apertures (not shown)accommodate temperature sensors. The presence of the feedthroughapertures 807 require the use of oxygen seals to keep oxygen out of theinternal cavities 812 of the thermal switches 800. In the illustratedembodiment, the top electrode 532 includes four ring-shaped oxygen seals890 as shown.

As shown, rectangular elastomer seals 890A are used in the oxygen seals890. This allows the larger differential expansion of the first andsecond plates 808, 810 to be accommodated by flexing of the seals 890(see above). Further in the illustrated embodiment, rectangular seals891 seal the first reservoir 824 and square seals 893 are used on bothsides of the dividing plate 842.

Precise thermal control of the top electrode 532 is critical, due to itsclose proximity to the wafer 502. To achieve precise thermal control ofthe top electrode 532, the local thermal conductivity of the thermalswitches 800 must be precisely controlled. A higher thermal conductivityresults in a lower thermal resistance (of the switch 800) and a lowerthermal conductivity results in a higher thermal resistance (of theswitch 800). Thus, a switch 800 in the on-state has a high thermalconductivity and a lower thermal resistance than a switch 800 in theoff-state. The largest source of variability in this thermalconductivity is variation in the gap height. The local thermalconductivity of a thermal switch 800 is inversely proportional to gapheight.

Practical limitations on achievable machining tolerances of the firstand second plates 808, 810 may result in surface flatness tolerances of0.002″ or greater on the gap defining surfaces. Consequently, a gap 820of nominal height 0.010″ may vary locally between 0.008″ and 0.012″,leading to +/−20% variation in local thermal conductivity.

To improve the precision of local thermal conductivity of the thermalswitches 800, the dividing plates 842 are shaped to create many discreteconduction zones 822. Thermal conduction occurs across the multitude ofconduction zones 822 rather than across a single ring-shaped gap. Sincethe thermal conductivity of each conduction zone 822 is proportional toarea, variations of the zone dimensions, l_(cz) and w_(cz), may be usedto adjust thermal conductivity and compensate for gap height variation.For example, as shown in FIG. 16F, the dividing plate 842 may haveconduction zones 822 with adjusted dimensions l_(cz′) and w_(cz″). Thevariation in gap height may be determined prior to assembly throughmeasurements of the surfaces of the first and second plates 808, 810using a coordinate measurement machine.

The method to create a thermally precise top electrode temperaturecontrol assembly 532 is:

-   -   1. Measure the surface profiles of the gap surfaces of the first        and second plates 808, 810 using a Coordinate Measuring Machine        (CMM),    -   2. Compute the as-assembled gap height for each thermal        conduction zone,    -   3. Adjust each zone's dimensions (l_(cz) and w_(cz)) to achieve        the desired zone thermal conductivity,    -   4. Laser cut dividing plates 842 with adjusted geometry, and    -   5. Assemble temperature control assembly 534 with the custom cut        dividing plates 842.

In one embodiment, the dividing plate 842 is manufactured by a lasercutting process and can be readily cut to custom dimensions to accountfor the manufacturing tolerances in each individual top electrodeassembly. The dimensions l_(cz) and w_(cz) may be cut with +/−0.001″accuracy using low-cost CO2 laser systems. A cutting accuracy of+/−0.001″ may lead to an accuracy of +/−0.8% in thermal conduction ofeach zone. If greater precision is required, more expensive lasercutting systems such as the Oxford Lasers E-Series laser micro cuttingsystem could be used to achieve dimensional accuracy of +/−0.0002″ andthermal conduction accuracy of +/−0.2%.

Electrostatic Chuck with Thermal Switches

The electrostatic chuck (ESC) of a Capacitively Coupled Plasma ProcessModule has two basic functions: (1) to “chuck” or clamp a silicon waferto a ceramic plate with electrostatic force and (2) to precisely controlthe temperature of the silicon wafer temperature to achieve an optimalresult during an etch process. Generally, the clamping function isaccomplished by applying a high voltage to a chucking electrode which iscommonly a thin metal sheet embedded in the ceramic plate. The clampingfunction holds the silicon wafer in place during etch and allows thebackside of the silicon wafer, i.e., the gap between the silicon waferand the top surface of the ESC) to be filled with helium at a pressurehigher than the chamber pressure. The pressurized helium serves toincrease the thermal conductivity across this gap.

With reference to FIGS. 17A and 17B, the basic structure of anelectrostatic chuck (ESC) 520 is shown. Generally, the ESC 520 includesan aluminum cooling plate 1002 having a plurality of cooling channels1004 for circulating coolant. The aluminum cooling plate 1002 serves asa base for the ESC 520. A ceramic plate 1006 contains embedded heaterelements or traces 1008 and a chucking electrode 1010. The heater traces1008 are commonly divided into ring shaped zones 1012. In theillustrated embodiment, the zones 1012 are powered independently toachieve desired temperature variation (edge hot, center hot, etc.). Theceramic plate 1006 is bonded to the cooling plate 1002 with a layer ofthermally conductive adhesive 1014. One or more apertures 1016 in thecooling plate 1002 allow passage of lifting pins (not shown, which maybe actuated up and down to lift the wafer), electrical connections,helium supply, etc.

As in the top electrode temperature control assembly 532, anelectrostatic chuck 520 controls temperature through a combination ofconstant cooling and modulated heating. The aluminum cooling plate 1002is typically maintained at a constant temperature. The thermallyconductive adhesive between the cooling plate 1002 and the ceramic plate1006 creates a prescribed thermal resistance (set by the thickness ofthe bond) such that a desired temperature differential will be achievedby one or both of the heat generated by the electric heater elements1008 in the ceramic plate 1002 or heat imparted to the wafer 502 by theplasma etch process.

But importantly, the thermal resistance between the cooling plate 1002and the ceramic plate 1006 is fixed. This forces compromises inefficiency, maximum plasma heat, rate of temperature change, andoperating temperature range.

In some etch processes, it is advantageous to perform a first etch stepat a first temperature, and then change the temperature of the wafer 502to a second lower or higher temperature at which a second etch step isperformed.

A retention device 510, such as an ESC 520, with liquid metal thermalswitches may achieve faster temperature changes by increasing thermalresistance during heating, so more of the heat generated by theelectrical heater goes into increasing the temperature of the ceramicplate, and decreasing thermal resistance during cooling so heat can bedrawn more quickly from the ceramic plate.

With reference to FIGS. 17C-17J, an exemplary retention devicetemperature control assembly 536 with thermal switches 1100 is shown.The retention device temperature control assembly 536 is located withinthe cooling plate 1002. In the illustrated embodiment, a variablethermal resistance may be achieved in the retention device or ESC 520 byplacing thermal switches 1100 within the retention device temperaturecooling assembly 536. In the illustrated embodiment, the retentiondevice 520 includes three toroidal or ring-shaped thermal switches1100A, 1100B, 1100C. Each thermal switch 1100A, 1100B, 1100C controls arespective ring-shaped zone 1012A, 1012B, 1012C.

In the illustrated embodiment, the cooling plate 1002 of the ESC 520includes a first plate 1002A and a second plate 1002B bolted togetherwith plastic shims 1102 therebetween. The top and bottom plates 1002A,1002B are composed from a thermally conductive material, such asaluminum. The bottom plate 1002B includes the cooling channels 1004. Theceramic plate 1006 contains the heater traces 1008 and the chuckingelectrode 1010 and is bonded to the cooling plate 1002 with a thin layerof thermally conductive silicone adhesive 1014. The layer of thermallyconductive silicone adhesive may be thinner than the layer of adhesiveused in a typical ESC, as the bulk of the thermal resistance between theceramic and cooling plate is replaced by the thermal resistance of thethermal switches 1100.

In the illustrated embodiment, the retention device temperature controlassembly 536 has a generally circular top and bottom surfaces 532A,532B. Each thermal switch 1100 is toroidal or ring shaped. In theillustrated embodiment, the retention device temperature controlassembly 536 includes first, second and third ring shaped concentricthermal switches 1100A, 1100B, 100C. Each thermal switch 1100A, 1100B,1100C is located adjacent, and controls the thermal resistance, in arespective ring-shaped portion or zone 1012A, 1012B, 1012C.

Each thermal switch 1100 includes first and second plates 1028A, 1028B,formed by, i.e., integral with, the top and bottom plates 1002A, 1002Bof the cooling plate 1002, respectively. In the illustrated embodiment,each thermal switch 1100 further includes a respective pneumaticactuator 1128. The first and second plates 1028A, 1028B are composedfrom a thermally conductive material and form respective internalcavities 1112. The internal cavity 1112 has one or more channels 1114that defines a gap or gaps 1120 (see below) between the first and secondplates 1002A, 1002B. Each thermal switch 1100 further includes areservoir 1124 coupled to the channel 1114 that contains a thermallyconductive liquid 1126. As shown, the pneumatic actuator 1128, of eachthermal switch 1100 is coupled to the first reservoir 1124 and thechannel 1114 and is moveable between a first state (shown in FIG. 17F)and a second state (shown in FIG. 17E) corresponding to the on-state andthe off-state of the thermal switch 1100, respectively. The pneumaticactuator 1128 is configured to allow the thermally conductive liquid1126 to flow from the reservoir 1124 to the channel 1114 when thepneumatic actuator 1128 is in the first state and to allow the thermallyconductive liquid 1126 to flow from the channel 1114 to the firstreservoir 1124 when the actuator 1128 is in the second state. Asdiscussed above, use of pneumatic actuators 1128 in place of solenoidsallows the separation between adjacent switch gaps to be reduced. In theillustrated embodiment, the bellows 1128B is located within the bottomplate 1002B. To further minimize the space between the switches 1100 inthe ESC 520, the bellows 1128B may be moved (or located) outside of thesecond plate 1002B.

Each pneumatic actuator 1128 includes a bellows 1128B and a plunger1128C. A source of pressurized air (not shown) is controllably coupledto the bellows 1128B. The plunger 1128C is coupled to the bellows 1128Band is moveable between first and second positions corresponding to thefirst and second states of the pneumatic actuators 1128, respectively.

In one embodiment, the bellows 1128B acts on the plunger 1128C to movethe plunger 1128C from the second position to the first position whenpressurized air from the source of pressurized air 1128A is applied tothe bellows 1128B. Further, a return spring 1128D may be coupled to thebellows 1128B and configured to move the plunger 1128C from the firstposition to the second position when the source of pressurized air isremoved from the bellows.

As shown in FIG. 17D, the plunger 1128C is held in place by linear ballbearings 1104 sliding on bearing posts 1102. Alternatively, the linearball bearings 1104 may be replaced by sleeve bearings, or the bellows1002B or the membrane 1140 may be configured to center the plunger1128C. The pneumatic actuator 1128 pushes the plunger 1128C to the firstposition (which forces the thermally conductive liquid 1126 into thegaps 1120A and 1120B). A pair of second (or gas) reservoirs 1136accommodate the gas displaced when thermally conductive liquid 1126moves into respective gaps 1120A and 1120B. In the illustratedembodiment, the second reservoirs 1136 are in the form of a circularchannels. Configuring each of the thermal switches 1100 with a pair ofgaps 1120A and 1120B allows a further reduction in the separationbetween adjacent thermal switch gaps.

Each thermal switch 1100 further includes a diaphragm or membrane 1140retained by clamp rings 1118A, 1118B and connected to the plunger 1198with a rib 1118C.

A dividing plate 1142 with laser scored vents provides the gas pathbetween the gap 1120 and the second reservoir 1136. In one embodiment,the dividing plate 1142 (and other plastic components of the thermalswitches 800) are composed from a polyimide material, such as Kaptonfilm available from 3M. Polyimide film has a CTE (20×10-6/° C.) close tothe CTE of aluminum (24×10-6/° C.). Since the dividing plate 1142 (andthe other plastic parts) are large (up to 12″ diameter, it is criticalthat thermal expansion be minimized.

It should be noted that in the illustrated embodiment, the gap 1120 ofeach thermal switch 1100 does not have sub-channels. The requiredthermal resistance may be achieved with a gap of length less than orequal to 0.2″, so a simple implementation as illustrated is best suitedto this embodiment. Oxygen seals 1190 and O-rings and/or square rings1192 are used to seal channels and cavities as needed.

In the illustrated embodiment, a plurality of feedthrough apertures 1016may be provided through the cooling plate 1002, and in some casesthrough the ceramic plate 1006 to permit passage of various featuresincluding, e.g., lift pins (not shown) which move the wafer up and downand electrical connections (not shown) to the chucking electrode 1010and/or heater traces 1008, and passage for gas (helium).

Precise control of local thermal conduction across the gaps 1120 isachieved using the same method as previously described for the topelectrode temperature control assembly. The dividing plates 1142 splitthe thermal switch gaps 1120 into a plurality of conduction zones 1122as shown in FIG. 17H.

In FIG. 17H, the retention device temperature control assembly 536(without the first plate 1002A) is show. In this view the plunger 1128Cof all three switches 1100A, 1100B, 1100C is down and the thermalswitches 1100A, 1100B, 1100C are all in the open position.

The size of the conduction zones is adjusted by modifying the dimensionsof the dividing plates. As previously discussed, the conduction zonesmay be adjusted to compensate for local variations in the thermal switchgap height. Further adjustments may be made to compensate for otherthermal variation, which in an ESC may be caused by:

-   -   Non-uniformity of cooling due to feedthroughs in the cooling        plate and the geometry of the cooling channels.    -   Manufacturing variation in heater elements, which lead to        deviation from the desired heater watt density and corresponding        hot or cold spots.    -   Variation in the thickness of the adhesive layer between the        ceramic plate and cooling plate.

In the illustrated embodiment of a retention device temperature controlassembly 536 with thermal switches 1100, all three of these variationscan be corrected by adjusting thermal conduction zones using the method:

-   -   1. Characterize the thermal resistance of the cooling plate.        This may, for example, be accomplished via thermal simulation.    -   2. Measure the thermal response of the as-manufactured ceramic        plate. For example, the embedded heater may be operated while        the ceramic plate is monitored with an infrared camera.    -   3. Measure the surfaces of the first, second, and ceramic plates        with a CMM.    -   4. Calculate the as-assembled switch gap.    -   5. Bond the ceramic to the first plate.    -   6. Measure the top surface of the bonded ceramic/first plate        assembly with a CMM.    -   7. Calculate the adhesive thickness.    -   8. Compute the required thermal conductivity of each conduction        zone.    -   9. Calculate the corresponding dimensions l_(cz) and w_(cz) of        each conduction zone.    -   10. Laser cut the dividing plates 1142 to the calculated        dimensions.    -   11. Assemble the retention device temperature control assembly        536.

Through use of this method, an ESC with thermal switches according tothe above embodiment may be able to achieve thermal precision superiorto that of a conventional ESC. Further, precise control of a prescribedspatial variation of local thermal conductivity could be achieved ifdesired, a capability not readily achieved using prior art.

For some embodiments of an ESC or other components which may benefitfrom thermal switches, it may be of further benefit that an intermediatethermal switch state has a distinct controlled spatial variation. A gapconfigured as shown in FIGS. 3P-R may be used to achieve a definitiveintermediate state (as opposed to intermediate states achieved throughpulsing). Further, multiple dividing plates (one additional dividingplate per intermediate state) may be implemented. In this fashion thespatial variation of thermal conductivity in the intermediary state maybe controlled.

In another embodiment as shown in FIGS. 17I and 17J, a temperaturecontrol assembly 1400 is configured with an un-switched (or always-on)thermal interface 1402. The temperature control assembly 1400 includes afirst plate 1408 and a second plate 1410. The first and second plates1408, 1410 are made from a thermally conductive material such asaluminum. The thermal interface 1402 is formed by one or more gaps 1420filled with a thermally conductive liquid (not shown). Multiple dividingplates 1442 in the gaps 1420 may be configured to achieve a desiredspatial variation of thermal resistance for the purposes of achieving adesired temperature profile of a working surface or workpiece. Thedesired dimensions of the conduction zones 1422 may be determined usingprocedures as described above. In the illustrated embodiment, the secondplate 1410 may include a plurality of cooling channels 1414. Thetemperature control assembly 1400 of FIGS. 17I and 17J may include oneor more of the features of the various devices described herein.

Passively Actuated Thermal Switch

In some thermal control applications, the requirements of a thermalswitch are such that passive actuation is sufficient or desirable. Forexample, in aerospace systems the available supply of electrical powermay be limited, making the power requirement of an active actuatorprohibitive. Other applications may require lower weight or cost thanthat achievable with an actively actuated thermal switch.

In some applications, a thermal control system needs only to maintain acomponent temperature in a relatively wide operating range. For example,acceptable operating temperatures for the battery of an electric vehiclemay be as wide as 10° C. to 60° C. This wide range combined with agreater emphasis on minimizing weight and cost may make a passivelyactuated switch, such as the embodiment illustrated in FIGS. 18A-18I,desirable. This embodiment might be employed in automotive thermalsystems including components such as a battery, battery charger,electric motor, power electronics, internal combustion engine, catalyticconverter, cabin HVAC, fuel cell, or thermoelectric generator.

In consideration of additional performance requirements in automotiveapplications, the illustrated embodiment includes design features toaddress:

-   -   (1) Operating temperatures below the freezing point of the        thermally conductive liquid—Gallium and alloys containing        gallium are known to expand when frozen and the thermal switch        must accommodate this expansion.    -   (2) Dynamic loading—Movement of the vehicle could cause the        thermally conductive liquid to slosh around within the switch,        resulting in an undesired increase in the thermal conductivity        of the switch if thermally conductive liquid is not withdrawn        from the gap.

It should be understood that these design features may be employed inactively actuated switches and in other types of thermal systems. Thethermal switch 1200 has a square housing and a toroidal or ring-shapedgap 1220, however, it should be noted that any shape, including anon-ring shaped gap 1220 may be used (similar to FIGS. 3A-3S).

With reference to FIGS. 18A-18I, a passively actuated thermal switch1200 with an on-state and an off-state has a first plate 1208 and asecond plate 1210 according to one embodiment of the present invention.The first and second plates 1208, 1210 are composed of a thermallyconductive material, such as aluminum. The first and second plates 1208,1210 of the thermal switch 1200 of the illustrated embodiment form ahousing that has a height of 0.7″ and a length and width of 3.5″. Thehousing 1208, 1210 includes apertures 1288 for mounting the thermalswitch 1200 and an exterior seal 1206 to keep out dirt and moisture.

The first and second plates 1208, 1210 are connected to form an internalcavity 1212 having a channel 1214 that forms a gap 1220 between thefirst and second plates 1208, 1210. The passively actuated thermalswitch 1200 includes a first reservoir 1224 coupled to the channel 1214.The first reservoir 1224 contains a thermally conductive liquid, such asmercury or an alloy of gallium, indium and tin. An actuating reservoir1202 contains an actuating material 1204 which expands with increasingtemperature. The choice of actuating material 1204 is dependent upon thedesired thermal performance of a specific switch design. The actuatingmaterial 1204 may be a material which expands on heating—such as ahydrocarbon grease, or a material which expands when melting—such asparaffin wax. A membrane 1240 is connected to the first and/or secondplates 1208, 1210. The membrane 1240 separates the first reservoir 1224from the actuating reservoir 1202 and is moveable between a first stateand a second state corresponding to the on-state and the off-state ofthe thermal switch 1200, respectively. The actuating material 1204expands when heated. Expansion of the actuating material 1204 causes themembrane 1240 to move from the second state to the first state. Thethermally conductive liquid 1226 flows from the first reservoir 1224 tothe channel 1214 when the membrane 1240 is in the first state and thethermally conductive liquid 1226 flows from the channel 1214 to thefirst reservoir 1224 when the membrane 1240 is in the second state.

As shown, the channel 1214 has a first end and a second end. The firstreservoir 1224 is coupled to the first end of the channel 1214. Thethermal switch 1200 includes a second reservoir 1236 coupled to thesecond end of the channel 1214. The second reservoir 1236 contains a gas(see above). A gas entry/exit point between the second reservoir 1236and the channel 1214 has a height of the entry/exit point that is lessthan a height of the gap 1220 (see above).

With particular reference to FIG. 18A-18F, the first plate 1208 isfastened to the second plate 1210 by a plurality of fasteners 1258.e.g., bolts. A plurality of plastic shims 1262 disposed between thefirst and second plates 1208, 1210 provide thermal isolation and allowthermal expansion of the first plate 1208 (relative to the second plate1210).

The membrane 1240 is composed of a suitable elastomer and separates thethermally conductive liquid 1226 from the actuating material 1204. Themembrane 1240 is secured to the second plate 1210 with a clamp ring1280. The clamp ring 1280 is secured with screws and clamps the membrane1240 to the second plate 1210. A support ring 1282 rests on a ledge inthe second plate 1210 and pushes the membrane 1240 diaphragm against thefirst plate 1208 when the thermal switch 1200 is assembled. A pluralityof seals 1284 (which may be O-rings or of rectangular or square crosssection) provide sealing at various locations in the thermal switch1200.

FIG. 18D is a cross-sectional view of the thermal switch 1200 along A-A(see FIG. 18C) and FIG. 18E is a cross-sectional view of the thermalswitch 1200 along B-B (see FIG. 18C). In the illustrated embodiment, thethermally conductive material 1226 is injected prior to the injection ofthe actuating material 1204. As shown in FIG. 18F, in the illustratedembodiment, the second plate 1210 includes two actuating material ports1203. The actuating material is injected through one of the ports 1203,while a vacuum pump evacuates the actuating reservoir via the other oneof the ports 1202 to minimize voids or gas pockets. As shown in FIG.18G, the first reservoir 1224 is filled with the thermally conductiveliquid 1226 using a port 1205.

Cross-sectional views of the thermal switch 1200 with the actuatingreservoir 1202 filled with the actuating material 1204 and the firstreservoir 1224 filled with the thermally conductive liquid 1226 areshown in FIGS. 18I and 18J. In the illustrated embodiment the thermallyconductive liquid 1226 is an alloy of gallium, indium and tin. Thethermal switch 1200 may include an oxygen seal 1290 (see above). Asdiscussed above, the oxygen seal 1290 may use a hydrocarbon vacuumgrease. The same grease may be used as the actuating material 1204. Theillustrated embodiment includes a separate trench for an oxygenabsorbing material. In other embodiments this trench may be omitted andan oxygen absorbing material may be added to the actuating material 1204or the gas blocking material 1260 of the oxygen seal.

In the illustrated embodiment the actuating reservoir 1202 is in thefirst plate 1208 which, in operation, has a higher temperature than thesecond plate 1210. Expansion of the grease causes pressure on themembrane 1240, which forces the thermally conductive liquid 1226 intothe gap 1220 and creates a higher thermal conductivity across the switch1200. With the actuating reservoir 1202 located in the hotter plate, theswitch 1200 begins to close (to a higher thermal conductivity, on-state)when the first plate 1208 is heated to a critical temperature. Thecritical temperature of a particular design may be set by choosing thevolume of the actuating reservoir 1202 and the volume of the actuatingmaterial 1204 in the actuating reservoir 1202.

It should be noted that the action of the switch 1200 closing andopening will be gradual and occur over a temperature range rather thanas an instantaneous change. Design parameters may be set to influencethe rate of change, including the ratio of gap volume to greasereservoir volume, or by adjusting the fill volume of actuating grease. Aphase changing material (such as melting paraffin wax or a boilingrefrigerant) may be used as an actuator if an abrupt switch actuation isdesired.

Aluminum plugs 1292 may be used to seal the actuating material orgrease, the gas blocking material 1260, and thermally conductive liquidin the respective reservoirs or volumes. Foam discs 1294 allow thesealing grease to expand and contract with temperature change. Anexternal seal 1206, which may be composed from an adhesive or anelastomer, has the purpose of keeping dirt out of the gap between thetop and bottom plates 1208, 1210.

With reference to FIGS. 18H and 18I, the thermal switch 1200 is shown inthe off and on-states, respectively. A plastic or insulating ring 1228is positioned to reduce heat flow in the off-state from the first plate1208 through the thermally conductive liquid 1226 outside the gap 1220,and down to the pedestal of the second plate 1210. This heat flow wouldincrease the thermal conductivity in the off-state, which may beundesirable.

A plastic vent ring 1218 with laser-cut vent slits provides a gas pathfrom the gap 1220 to the second reservoir 1236. As discussed above, thesecond or gas reservoir 1236 may have a volume much larger than the gap1220. Thus, the increase in gas pressure as the thermally conductiveliquid 1226 advances into the gap 1220 is relatively small. In theactively actuated embodiments, this was done to reduce the requiredactuator force. The expansion of the actuating material 1204 cangenerate very high pressure if constrained, but it may be desirable tominimize the actuating pressure, as this pressure would also act on theseal at the perimeter of the actuating reservoir and on the first andsecond plates 1208, 1210 potentially creating a high bolt load.

In one embodiment, to make the switch 1200 capable of operation belowthe freezing point of the thermally conductive liquid, the thermallyconductive liquid 1226 is confined to a toroidal volume bounded by thefirst plate 1208, pedestal of the second plate 1210, and diaphragm 1240.When the thermally conductive liquid 1226 freezes, it is free to expandoutwards. The membrane 1240 may flex outwards to accommodate theexpansion. Cooling of the actuating material 1204 to the freezetemperature of the thermally conductive liquid 1226 will have createdsufficient empty volume to accommodate expansion of the thermallyconductive liquid 1226. The elastomer cap 1241 keeps the thermallyconductive liquid 1226 out of the fill port 1225.

The thermal switch 1200 will be subjected to dynamic loading which maycause the pressure in the thermally conductive liquid in contact withthe gas entry/exit point to increase. To prevent the thermallyconductive liquid from flowing into the second reservoir, achieving aminimum gap height at the gas exit/entry point is important. Compressionof a backing ring 1284A forces the vent ring 1218 firmly against thefirst plate 1208. This ideally means only the laser cut slits (or gasvents) are available as flow paths.

Dynamic loading may also lead to the thermally conductive liquid 1226sloshing in the gap 1220. In some circumstances this may lead to aportion of liquid becoming separated from the remaining liquid in thefirst reservoir. In the illustrated embodiment, the gap 1220 is sloped.As explained above and illustrated in FIGS. 3M-3O, in a sloped gapsurface tension will always exert a net expelling force on any thermallyconductive liquid 1226. Thus, the sloped gap ensures both consistentactuation of the switch and that no liquid will be in the gap if theswitch freezes.

The embodiment described above is an example of a thermal switchpassively actuated by the expansion of a liquid or grease. In light ofall of the previously discussed embodiments, features of variousembodiments may be combined or modified to achieve passive actuation byother means. Shape memory alloy springs may be employed to actuate theplunger, in place of the solenoid, in an embodiment similar to FIG.6A-6N. Shape memory alloys are materials which may generate force from acrystallographic phase change occurring at a critical temperature. Ifthe compression springs 208 are replaced with shape memory alloysprings, the force applied by the spring would vary depending on thetemperature of the spring, with actuating force being achieved at thephase transformation temperature of the particular shape memory alloychosen. With reference to the embodiment of FIGS. 5A and 5B, abimetallic element (two metals of dissimilar thermal expansion joined toform a thermostatic structure) such as a prestrained Belleville washer,a stack of bimetallic washers, a bimetallic strip or ring, may beconfigured as actuator 128. The actuating temperature could be chosen byappropriate selection of bimetal materials. With reference to theembodiment of FIG. 15A-15B, the bellows 728B may be sealed and chargedwith a refrigerant. Actuation of the switch would occur at the boilingtemperature of the refrigerant.

Generally, the embodiments discussed in detail above are normally openswitches, i.e., the switches are open, i.e., have lower thermalconductivity when the actuator is inactive (not actuated). It should benoted that each of the embodiments may be configured as normally closedswitches, i.e., have lower thermal conductively when the actuator isactive (actuated).

Reference throughout this specification to “one embodiment”, “anembodiment”, “one example” or “an example” means that a particularfeature, structure or characteristic described in connection with theembodiment or example is included in at least one embodiment of thepresent invention. Thus, appearances of the phrases “in one embodiment”,“in an embodiment”, “one example” or “an example” in various placesthroughout this specification are not necessarily all referring to thesame embodiment or example. Furthermore, the particular features,structures or characteristics may be combined in any suitablecombinations and/or sub-combinations in one or more embodiments orexamples. In addition, it is appreciated that the figures providedherewith are for explanation purposes to persons ordinarily skilled inthe art and that the drawings are not necessarily drawn to scale.Several (or different) elements discussed below, and/or claimed, aredescribed as being “coupled” or “connected” or the like. Thisterminology is intended to be non-limiting.

The above description of illustrated examples of the present invention,including what is described in the Abstract, are not intended to beexhaustive or to be limitation to the precise forms disclosed. Whilespecific embodiments of, and examples for, the invention are describedherein for illustrative purposes, various equivalent modifications arepossible without departing from the broader spirit and scope of thepresent invention.

It is to be appreciated that the terms “include,” “includes,” and“including” have the same meaning as the terms “comprise,” “comprises,”and “comprising.”

Several embodiments have been discussed in the foregoing description.However, the embodiments discussed herein are not intended to beexhaustive or limit the invention to any particular form. Theterminology which has been used is intended to be in the nature of wordsof description rather than of limitation. Many modifications andvariations are possible in light of the above teachings and theinvention may be practiced otherwise than as specifically described.

Obviously, many modifications and variations of the present inventionare possible in light of the above teachings. The invention may bepracticed otherwise than as specifically described within the scope ofthe appended claims.

What is claimed is:
 1. A thermal device for controlling a temperatureassociated with a controlled component, comprising: a thermal switchhaving an on-state and an off-state; and, a heat sink, the thermalswitch further including: a first plate being composed from a thermallyconductive material and being thermally coupled to the controlledcomponent; a second plate being composed from a thermally conductivematerial, the first and second plates being connected to form aninternal cavity having a channel defining a gap between the first andsecond plate, the heat sink being coupled to the second plate; a firstreservoir coupled to the channel, the first reservoir containing athermally conductive liquid; and, an actuator coupled to the firstreservoir and the channel, the actuator being moveable between a firststate and a second state corresponding to the on-state and the off-stateof the thermal switch, respectively, and being configured to allow thethermally conductive liquid to flow from the reservoir to the channelwhen the actuator is in the first state and to allow the thermallyconductive liquid to flow from the channel to the first reservoir whenthe actuator is in the second state.
 2. A thermal device, as set forthin claim 1, wherein the heat sink is an external heat sink fastened toan external surface of the second plate.
 3. A thermal device, as setforth in claim 2, wherein the heat sink is air cooled.
 4. A thermaldevice, as set forth in claim 2, wherein the heat sink is liquid cooled.5. A thermal device, as set forth in claim 1, wherein the controlledcomponent is a thermoelectric cooler connected an external surface ofthe first plate.
 6. A thermal device, as set forth in claim 1, whereinthe controlled component is a heat source.
 7. A thermal device, as setforth in claim 6, wherein the controlled component is a heat pipe.
 8. Athermal device, as set forth in claim 1, wherein the controlledcomponent is a liquid-based thermal coupling device.
 9. A thermaldevice, as set forth in claim 1, wherein the heat sink includes one ormore cooling channels embedded in the second plate.
 10. A thermaldevice, as set forth in claim 1, wherein the controlled component is aheat generating component.
 11. A thermal device, as set forth in claim1, further comprising a heating device coupled between the first plateand the controlled component.
 12. A thermal device as set forth in claim11, wherein the heating device is one of a film heater, a strip heaterand a cast heater.
 13. A thermal device, as set forth in claim 1,further comprising a first liquid based coupling device coupled to thefirst plate, wherein the heat sink includes a second liquid basedcoupling device coupled to the second plate, the first and second liquidbased coupling devices and the thermal switch forming a variableliquid-liquid heat exchanger.
 14. A thermal device, comprising: athermoelectric cooler; a thermal switch having an on-state and anoff-state; and, a heat sink, the thermal switch further including: afirst plate being composed from a thermally conductive material andbeing thermally coupled to the thermoelectric cooler; a second platebeing composed from a thermally conductive material, the first andsecond plates being connected to form an internal cavity having achannel defining a gap between the first and second plate and beingcoupled to the heat sink; a first reservoir coupled to the channel, thefirst reservoir containing a thermally conductive liquid; and, anactuator coupled to the first reservoir and the channel, the actuatorbeing moveable between a first state and a second state corresponding tothe on-state and the off-state of the thermal switch, respectively, andbeing configured to allow the thermally conductive liquid to flow fromthe reservoir to the channel when the actuator is in the first state andto allow the thermally conductive liquid to flow from the channel to thefirst reservoir when the actuator is in the second state.
 15. A thermaldevice for controlling a temperature associated with a heat source,comprising: a thermal switch having an on-state and an off-state; and, aplurality of cooling channels in the second plate acting as a heat sink,the thermal switch further including: a first plate being composed froma thermally conductive material and being coupled to the heat source; asecond plate being composed from a thermally conductive material, thefirst and second plates being connected to form an internal cavityhaving a channel defining a gap between the first and second plate, theplurality of cooling channels being located within the second plate andacting as a heat sink; a first reservoir coupled to the channel, thefirst reservoir containing a thermally conductive liquid; an actuatorcoupled to the first reservoir and the channel, the actuator beingmoveable between a first state and a second state corresponding to theon-state and the off-state of the thermal switch, respectively, andbeing configured to allow the thermally conductive liquid to flow fromthe reservoir to the channel when the actuator is in the first state andto allow the thermally conductive liquid to flow from the channel to thefirst reservoir when the actuator is in the second state.
 16. A thermaldevice for controlling a temperature associated with a workpiece,comprising: a heating device coupled to the workpiece; a thermal switchhaving an on-state and an off-state; and, a plurality of coolingchannels, the thermal switch further including: a first plate beingcomposed from a thermally conductive material and being coupled to theheating device; a second plate being composed from a thermallyconductive material, the first and second plates being connected to forman internal cavity having a channel defining a gap between the first andsecond plate, the plurality of cooling channels being located within thesecond plate and acting as a heat sink; a first reservoir coupled to thechannel, the first reservoir containing a thermally conductive liquid;an actuator coupled to the first reservoir and the channel, the actuatorbeing moveable between a first state and a second state corresponding tothe on-state and the off-state of the thermal switch, respectively, andbeing configured to allow the thermally conductive liquid to flow fromthe reservoir to the channel when the actuator is in the first state andto allow the thermally conductive liquid to flow from the channel to thefirst reservoir when the actuator is in the second state.
 17. A thermaldevice, as set forth in claim 16, wherein the heating device is one of afilm heater, a strip heater and a cast heater.
 18. A thermal device,comprising: a thermal switch having an on-state and an off-state; and, afirst liquid-based thermal coupling device, the thermal switch furtherincluding: a first plate being composed from a thermally conductivematerial and being thermally coupled to the first liquid-based thermalcoupling device; a second plate being composed from a thermallyconductive material, the first and second plates being connected to forman internal cavity having a channel defining a gap between the first andsecond plate; a first reservoir coupled to the channel, the firstreservoir containing a thermally conductive liquid; and, an actuatorcoupled to the first reservoir and the channel, the actuator beingmoveable between a first state and a second state corresponding to theon-state and the off-state of the thermal switch, respectively, andbeing configured to allow the thermally conductive liquid to flow fromthe reservoir to the channel when the actuator is in the first state andto allow the thermally conductive liquid to flow from the channel to thefirst reservoir when the actuator is in the second state; and, a secondliquid-based thermal coupling device coupled to the second plate, thefirst and second liquid-based thermal coupling devices and the thermalswitch forming a variable liquid-liquid heat exchanger.